九州大学 研究者情報
論文一覧
川越 清以(かわごえ きよとも) データ更新日:2018.08.21

教授 /  理学研究院 物理学部門 基礎粒子系物理学


原著論文
1. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, M. Abolins, O. S. Abouzeid, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, G. Alimonti, L. Alio, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, A search for an excited muon decaying to a muon and two jets in pp collisions at √ s = 8 TeV with the ATLAS detector, New Journal of Physics, 10.1088/1367-2630/18/7/073021, 18, 7, 2016.07, [URL], Anew search signature for excited leptons is explored. Excited muons are sought in the channel pp → μμ∗→ μμ jet jet, assuming both the production and decay occur via a contact interaction. The analysis is based on 20.3 fb-1 of pp collision data at a centre-of-mass energy of s = 8 TeV taken with the ATLAS detector at the large hadron collider. No evidence of excited muons is found, and limits are set at the 95% confidence level on the cross section times branching ratio as a function of the excited-muonmass μμ∗. For μμ∗between 1.3 and 3.0 TeV, the upper limit on φB (μ∗→ μqq) is between 0.6 and 1 fb. Limits on sB are converted to lower bounds on the compositeness scale. In the limiting case L = μμ∗, excitedmuonswith amass below2.8 TeVare excluded.With the samemodel assumptions, these limits at larger μ∗masses improve upon previous limits fromtraditional searches based on the gauge-mediated decay μ∗→ μγ..
2. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, M. Abolins, O. S. AbouZeid, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, G. Alimonti, L. Alio, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for single production of vector-like quarks decaying into Wb in pp collisions at √s = 8 TeV with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4281-8, 76, 8, 2016.08, [URL], A search for singly produced vector-like Q quarks, where Q can be either a T quark with charge + 2 / 3 or a Y quark with charge - 4 / 3 , is performed in proton–proton collisions recorded with the ATLAS detector at the LHC. The dataset corresponds to an integrated luminosity of 20.3 fb- 1 and was produced with a centre-of-mass energy of s=8 TeV. This analysis targets Q→ Wb decays where the W boson decays leptonically. A veto on massive large-radius jets is used to reject the dominant tt¯ background. The reconstructed Q-candidate mass, ranging from 0.4 to 1.2 TeV, is used in the search to discriminate signal from background processes. No significant deviation from the Standard Model expectation is observed, and limits are set on the Q→ Wb cross-section times branching ratio. The results are also interpreted as limits on the QWb coupling and the mixing with the Standard Model sector for a singlet T quark or a Y quark from a doublet. T quarks with masses below 0.95 TeV are excluded at 95 % confidence level, assuming a unit coupling and a BR(T→ Wb) = 0.5 , whereas the expected limit is 1.10 TeV..
3. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for pair production of gluinos decaying via stop and sbottom in events with b -jets and large missing transverse momentum in pp collisions at s =13 TeV with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.94.032003, 94, 3, 2016.08, [URL], A search for supersymmetry involving the pair production of gluinos decaying via third-generation squarks to the lightest neutralino (χ10) is reported. It uses an LHC proton-proton data set at a center-of-mass energy s=13 TeV with an integrated luminosity of 3.2 fb-1 collected with the ATLAS detector in 2015. The signal is searched for in events containing several energetic jets, of which at least three must be identified as b jets, large missing transverse momentum, and, potentially, isolated electrons or muons. Large-radius jets with a high mass are also used to identify highly boosted top quarks. No excess is found above the predicted background. For χ10 masses below approximately 700 GeV, gluino masses of less than 1.78 TeV and 1.76 TeV are excluded at the 95% C.L. in simplified models of the pair production of gluinos decaying via sbottom and stop, respectively. These results significantly extend the exclusion limits obtained with the s=8 TeV data set..
4. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at s =13 TeV using the ATLAS detector, Physical Review D, 10.1103/PhysRevD.94.032005, 94, 3, 2016.08, [URL], Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an integrated luminosity of 3.2 fb-1 at s=13 TeV collected in 2015 with the ATLAS detector at the Large Hadron Collider. Events are required to have at least one jet with a transverse momentum above 250 GeV and no leptons. Several signal regions are considered with increasing missing-transverse-momentum requirements between ETmiss>250 GeV and ETmiss>700 GeV. Good agreement is observed between the number of events in data and Standard Model predictions. The results are translated into exclusion limits in models with large extra spatial dimensions, pair production of weakly interacting dark-matter candidates, and the production of supersymmetric particles in several compressed scenarios..
5. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, �kesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for charged Higgs bosons produced in association with a top quark and decaying via H� → τν using pp collision data recorded at √s = 13 TeV by the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.06.017, 759, 555-574, 2016.08, [URL], Charged Higgs bosons produced in association with a single top quark and decaying via H� → τν are searched for with the ATLAS experiment at the LHC, using proton-proton collision data at √s = 13 TeV corresponding to an integrated luminosity of 3.2 fb-1. The final state is characterised by the presence of a hadronic r decay and missing transverse momentum, as well as a hadronically decaying top quark, resulting in the absence of high-transverse-momentum electrons and muons. The data are found to be consistent with the expected background from Standard Model processes. A statistical analysis leads to 95% confidence-level upper limits on the production cross section times branching fraction, σ(pp → [b]tH�) � BR (H� → τν), between 1.9 pb and 15 fb, for charged Higgs boson masses ranging from 200 to 2000 GeV. The exclusion limits for this search surpass those obtained with the proton-proton collision data recorded at √s = 8 TeV..
6. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for charged Higgs bosons produced in association with a top quark and decaying via H± → τν using pp collision data recorded at √s = 13 TeV by the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.06.017, 759, 555-574, 2016.08, [URL], Charged Higgs bosons produced in association with a single top quark and decaying via H± → τν are searched for with the ATLAS experiment at the LHC, using proton-proton collision data at √s = 13 TeV corresponding to an integrated luminosity of 3.2 fb-1. The final state is characterised by the presence of a hadronic r decay and missing transverse momentum, as well as a hadronically decaying top quark, resulting in the absence of high-transverse-momentum electrons and muons. The data are found to be consistent with the expected background from Standard Model processes. A statistical analysis leads to 95% confidence-level upper limits on the production cross section times branching fraction, σ(pp → [b]tH±) × BR (H± → τν), between 1.9 pb and 15 fb, for charged Higgs boson masses ranging from 200 to 2000 GeV. The exclusion limits for this search surpass those obtained with the proton-proton collision data recorded at √s = 8 TeV..
7. , , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurements of the Higgs boson production and decay rates and constraints on its couplings from a combined ATLAS and CMS analysis of the LHC pp collision data at √s = 7 and 8 TeV, Journal of High Energy Physics, 10.1007/JHEP08(2016)045, 2016, 8, 2016.08, [URL], Combined ATLAS and CMS measurements of the Higgs boson production and decay rates, as well as constraints on its couplings to vector bosons and fermions, are presented. The combination is based on the analysis of five production processes, namely gluon fusion, vector boson fusion, and associated production with a W or a Z boson or a pair of top quarks, and of the six decay modes H → ZZ, W W, γγ, ττ, bb, and μμ. All results are reported assuming a value of 125.09 GeV for the Higgs boson mass, the result of the combined measurement by the ATLAS and CMS experiments. The analysis uses the CERN LHC proton-proton collision data recorded by the ATLAS and CMS experiments in 2011 and 2012, corresponding to integrated luminosities per experiment of approximately 5 fb−1 at √s = 7 TeV and 20 fb−1 at √s = 8 TeV. The Higgs boson production and decay rates measured by the two experiments are combined within the context of three generic parameterisations: two based on cross sections and branching fractions, and one on ratios of coupling modifiers. Several interpretations of the measurements with more model-dependent parameterisations are also given. The combined signal yield relative to the Standard Model prediction is measured to be 1.09 ± 0.11. The combined measurements lead to observed significances for the vector boson fusion production process and for the H → ττ decay of 5.4 and 5.5 standard deviations, respectively. The data are consistent with the Standard Model predictions for all parameterisations considered..
8. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, M. Abolins, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurements of the charge asymmetry in top-quark pair production in the dilepton final state at s =8 TeV with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.94.032006, 94, 3, 2016.08, [URL], Measurements of the top-antitop quark pair production charge asymmetry in the dilepton channel, characterized by two high-pT leptons (electrons or muons), are presented using data corresponding to an integrated luminosity of 20.3 fb-1 from pp collisions at a center-of-mass energy s=8 TeV collected with the ATLAS detector at the Large Hadron Collider at CERN. Inclusive and differential measurements as a function of the invariant mass, transverse momentum, and longitudinal boost of the tt system are performed both in the full phase space and in a fiducial phase space closely matching the detector acceptance. Two observables are studied: ACℓℓ based on the selected leptons and ACtt based on the reconstructed tt final state. The inclusive asymmetries are measured in the full phase space to be ACℓℓ=0.008±0.006 and ACtt=0.021±0.016, which are in agreement with the Standard Model predictions of ACℓℓ=0.0064±0.0003 and ACtt=0.0111±0.0004..
9. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, M. Abolins, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of the inclusive isolated prompt photon cross section in pp collisions at s=8TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP08(2016)005, 2016, 8, 2016.08, [URL], Abstract: A measurement of the cross section for the inclusive production of isolated prompt photons in proton-proton collisions at a centre-of-mass energy of s=8 TeV is presented. The measurement covers the pseudorapidity ranges |ηγ | < 1.37 and 1.56 ≤ |ηγ | < 2.37 in the transverse energy range 25 < ET γ < 1500 GeV. The results are based on an integrated luminosity of 20.2 fb−1, recorded by the ATLAS detector at the LHC. Photon candidates are identified by combining information from the calorimeters and the inner tracker. The background is subtracted using a data-driven technique, based on the observed calorimeter shower-shape variables and the deposition of hadronic energy in a narrow cone around the photon candidate. The measured cross sections are compared with leading-order and next-to-leading order perturbative QCD calculations and are found to be in a good agreement over ten orders of magnitude.[Figure not available: see fulltext.].
10. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of the double-differential high-mass Drell-Yan cross section in pp collisions at √s = 8 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP08(2016)009, 2016, 8, 2016.08, [URL], This paper presents a measurement of the double-differential cross section for the Drell-Yan Z/γ → ℓ+ and photon-induced γγ → ℓ+ processes where ℓ is an electron or muon. The measurement is performed for invariant masses of the lepton pairs, mℓℓ, between 116 GeV and 1500 GeV using a sample of 20.3 fb−1 of pp collisions data at centre-of-mass energy of s=8 TeV collected by the ATLAS detector at the LHC in 2012. The data are presented double differentially in invariant mass and absolute dilepton rapidity as well as in invariant mass and absolute pseudorapidity separation of the lepton pair. The single-differential cross section as a function of mℓℓ is also reported. The electron and muon channel measurements are combined and a total experimental precision of better than 1% is achieved at low mℓℓ. A comparison to next-to-next-to-leading order perturbative QCD predictions using several recent parton distribution functions and including next-to-leading order electroweak effects indicates the potential of the data to constrain parton distribution functions. In particular, a large impact of the data on the photon PDF is demonstrated.[Figure not available: see fulltext.].
11. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of the angular coefficients in Z-boson events using electron and muon pairs from data taken at √s = 8 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP08(2016)159, 2016, 8, 2016.08, [URL], The angular distributions of Drell-Yan charged lepton pairs in the vicinity of the Z-boson mass peak probe the underlying QCD dynamics of Z-boson production. This paper presents a measurement of the complete set of angular coefficients A0−7 describing these distributions in the Z-boson Collins-Soper frame. The data analysed correspond to 20.3 fb−1 of pp collisions at s=8 TeV, collected by the ATLAS detector at the CERN LHC. The measurements are compared to the most precise fixed-order calculations currently available (O(αs2)) and with theoretical predictions embedded in Monte Carlo generators. The measurements are precise enough to probe QCD corrections beyond the formal accuracy of these calculations and to provide discrimination between different parton-shower models. A significant deviation from the (O(αs2)) predictions is observed for A0 − A2. Evidence is found for non-zero A5,6,7, consistent with expectations.[Figure not available: see fulltext.].
12. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, R. Aben, M. Abolins, O. S. AbouZeid, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, G. Alimonti, L. Alio, J. Alison, S. P. Alkire, B. M.M. Allbrooke, P. P. Allport, A. Aloisio, A. Alonso, F. Alonso, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of the CP-violating phase ϕsand the Bs 0meson decay width difference with Bs 0→ J/ψϕ decays in ATLAS, Journal of High Energy Physics, 10.1007/JHEP08(2016)147, 2016, 8, 2016.08, [URL], A measurement of the Bs 0decay parameters in the Bs 0→ J/ψϕ channel using an integrated luminosity of 14.3 fb−1collected by the ATLAS detector from 8 TeV pp collisions at the LHC is presented. The measured parameters include the CP -violating phase ϕs, the decay width Γs and the width difference between the mass eigenstates ΔΓs. The values measured for the physical parameters are statistically combined with those from 4.9 fb−1of 7 TeV data, leading to the following: Φs = -0.090 ± 0.078 (stat.) ± (syst.) rad Δ Γs = 0.085 ± 0.011 (stat.) ± 0.007 (syst.) Ps-1 Δ Γs = 0.675 ± 0.003 (stat.) ± 0.03 (syst.) Ps-1 In the analysis the parameter ΔΓs is constrained to be positive. Results for ϕs and ΔΓs are also presented as 68% and 95% likelihood contours in the ϕs-ΔΓs plane. Also measured in this decay channel are the transversity amplitudes and corresponding strong phases. All measurements are in agreement with the Standard Model predictions.[Figure not available: see fulltext.].
13. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, M. Abolins, O. S. AbouZeid, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, A. Alonso, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of fiducial differential cross sections of gluon-fusion production of Higgs bosons decaying to WW →eνμν with the ATLAS detector at √s=8 TeV, Journal of High Energy Physics, 10.1007/JHEP08(2016)104, 2016, 8, 2016.08, [URL], This paper describes a measurement of fiducial and differential cross sections of gluon-fusion Higgs boson production in the H → W W→ eνμν channel, using 20.3 fb−1 of proton-proton collision data. The data were produced at a centre-of-mass energy of s=8 TeV at the CERN Large Hadron Collider and recorded by the ATLAS detector in 2012. Cross sections are measured from the observed H→ W W→ eνμν signal yield in categories distinguished by the number of associated jets. The total cross section is measured in a fiducial region defined by the kinematic properties of the charged leptons and neutrinos. Differential cross sections are reported as a function of the number of jets, the Higgs boson transverse momentum, the dilepton rapidity, and the transverse momentum of the leading jet. The jet-veto efficiency, or fraction of events with no jets above a given transverse momentum threshold, is also reported. All measurements are compared to QCD predictions from Monte Carlo generators and fixed-order calculations, and are in agreement with the Standard Model predictions.[Figure not available: see fulltext.].
14. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of exclusive γγ →w+W- production and search for exclusive Higgs boson production in pp collisions at s =8 TeV using the ATLAS detector, Physical Review D, 10.1103/PhysRevD.94.032011, 94, 3, 2016.08, [URL], Searches for exclusively produced W boson pairs in the process pp(γγ)→pW+W-p and an exclusively produced Higgs boson in the process pp(gg)→pHp have been performed using e±μ final states. These measurements use 20.2 fb-1 of pp collisions collected by the ATLAS experiment at a center-of-mass energy s=8 TeV at the LHC. Exclusive production of W+W- consistent with the Standard Model prediction is found with 3.0σ significance. The exclusive W+W- production cross section is determined to be σ(γγ→W+W-→e±μX)=6.9±2.2(stat)±1.4(sys) fb, in agreement with the Standard Model prediction. Limits on anomalous quartic gauge couplings are set at 95% confidence level as -1.7×10-6
15. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of W± and Z-boson production cross sections in pp collisions at s=13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.06.023, 759, 601-621, 2016.08, [URL], Measurements of the W±→ℓ±ν and Z→ℓ+ production cross sections (where ℓ±=e±±) in proton–proton collisions at s=13 TeV are presented using data recorded by the ATLAS experiment at the Large Hadron Collider, corresponding to a total integrated luminosity of 81 pb−1. The total inclusive W±-boson production cross sections times the single-lepton-flavour branching ratios are σW+ tot=11.83±0.02 (stat)±0.32 (sys)±0.25 (lumi) nb and σW tot=8.79±0.02 (stat)±0.24 (sys)±0.18 (lumi) nb for W+ and W, respectively. The total inclusive Z-boson production cross section times leptonic branching ratio, within the invariant mass window 66ℓℓ<116 GeV, is σZ tot=1.981±0.007 (stat)±0.038 (sys)±0.042 (lumi) nb. The W+, W, and Z-boson production cross sections and cross-section ratios within a fiducial region defined by the detector acceptance are also measured. The cross-section ratios benefit from significant cancellation of experimental uncertainties, resulting in σW+ fidW fid=1.295±0.003 (stat)±0.010 (sys) and σW± fidZ fid=10.31±0.04 (stat)±0.20 (sys). Theoretical predictions, based on calculations accurate to next-to-next-to-leading order for quantum chromodynamics and to next-to-leading order for electroweak processes and which employ different parton distribution function sets, are compared to these measurements..
16. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Study of the rare decays of Bs0 and B0 into muon pairs from data collected during the LHC Run 1 with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4338-8, 76, 9, 2016.09, [URL], A study of the decays Bs0→μ+μ- and B0→ μ+μ- has been performed using data corresponding to an integrated luminosity of 25 fb- 1 of 7 and 8 TeV proton–proton collisions collected with the ATLAS detector during the LHC Run 1. For the B0 dimuon decay, an upper limit on the branching fraction is set at B(B0→ μ+μ-) < 4.2 × 10 - 10 at 95 % confidence level. For Bs0, the branching fraction B(Bs0→μ+μ-)=(0.9-0.8+1.1)×10-9 is measured. The results are consistent with the Standard Model expectation with a p value of 4.8 %, corresponding to 2.0 standard deviations..
17. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Searches for heavy diboson resonances in pp collisions at √s=13 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP09(2016)173, 2016, 9, 2016.09, [URL], Searches for new heavy resonances decaying to WW, WZ, and ZZ bosons are presented, using a data sample corresponding to 3.2 fb−1 of pp collisions at s=13 TeV collected with the ATLAS detector at the CERN Large Hadron Collider. Analyses selecting ννqq, ℓνqq, ℓℓqq and qqqq final states are combined, searching for an arrow-width resonance with mass between 500 and 3000 GeV. The discriminating variable is either an invariant mass or a transverse mass. No significant deviations from the Standard Model predictions are observed. Three benchmark models are tested: a model predicting the existence of a new heavy scalar singlet, a simplified model predicting a heavy vector-boson triplet, and a bulk Randall-Sundrum model with a heavy spin-2 graviton. Cross-section limits are set at the 95% confidence level and are compared to theoretical cross-section predictions for a variety of models. The data exclude a scalar singlet with mass below 2650 GeV, a heavy vector-boson triplet with mass below 2600 GeV, and a graviton with mass below 1100 GeV. These results significantly extend the previous limits set using pp collisions at s=8 TeV.[Figure not available: see fulltext.].
18. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for top squarks in final states with one isolated lepton, jets, and missing transverse momentum in s =13 TeV pp collisions with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.94.052009, 94, 5, 2016.09, [URL], The results of a search for the top squark, the supersymmetric partner of the top quark, in final states with one isolated electron or muon, jets, and missing transverse momentum are reported. The search uses the 2015 LHC pp collision data at a center-of-mass energy of s=13 TeV recorded by the ATLAS detector and corresponding to an integrated luminosity of 3.2 fb-1. The analysis targets two types of signal models: gluino-mediated pair production of top squarks with a nearly mass-degenerate top squark and neutralino and direct pair production of top squarks, decaying to the top quark and the lightest neutralino. The experimental signature in both signal scenarios is similar to that of a top quark pair produced in association with large missing transverse momentum. No significant excess over the Standard Model background prediction is observed, and exclusion limits on gluino and top squark masses are set at 95% confidence level. The results extend the LHC run-1 exclusion limit on the gluino mass up to 1460 GeV in the gluino-mediated scenario in the high gluino and low top squark mass region and add an excluded top squark mass region from 745 to 780 GeV for the direct top squark model with a massless lightest neutralino. The results are also reinterpreted to set exclusion limits in a model of vectorlike top quarks..
19. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for supersymmetry in a final state containing two photons and missing transverse momentum in √s = 13 TeV pp collisions at the LHC using the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4344-x, 76, 9, 2016.09, [URL], A search has been made for supersymmetry in a final state containing two photons and missing transverse momentum using the ATLAS detector at the Large Hadron Collider. The search makes use of 3.2fb-1 of proton-proton collision data collected at a centre-of-mass energy of 13 TeV in 2015. Using a combination of data-driven and Monte-Carlo-based approaches, the Standard Model background is estimated to be 0.27-0.10+0.22 events. No events are observed in the signal region; considering the expected background and its uncertainty, this observation implies a model-independent 95 % CL upper limit of 0.93 fb (3.0 events) on the visible cross section due to physics beyond the Standard Model. In the context of a generalized model of gauge-mediated supersymmetry breaking with a bino-like next-to-lightest supersymmetric particle, this leads to a lower limit of 1650 GeV on the mass of a degenerate octet of gluino states, independent of the mass of the lighter bino-like neutralino..
20. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for resonances in diphoton events at √s=13 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP09(2016)001, 2016, 9, 2016.09, [URL], Searches for new resonances decaying into two photons in the ATLAS experiment at the CERN Large Hadron Collider are described. The analysis is based on proton-proton collision data corresponding to an integrated luminosity of 3.2 fb−1 at s=13 TeV recorded in 2015. Two searches are performed, one targeted at a spin-2 particle of mass larger than 500 GeV, using Randall-Sundrum graviton states as a benchmark model, and one optimized for a spin-0 particle of mass larger than 200 GeV. Varying both the mass and the decay width, the most significant deviation from the background-only hypothesis is observed at a diphoton invariant mass around 750 GeV with local significances of 3.8 and 3.9 standard deviations in the searches optimized for a spin-2 and spin-0 particle, respectively. The global significances are estimated to be 2.1 standard deviations for both analyses. The consistency between the data collected at 13 TeV and 8 TeV is also evaluated. Limits on the production cross section times branching ratio to two photons for the two resonance types are reported.[Figure not available: see fulltext.].
21. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for pair production of Higgs bosons in the bbbb final state using proton-proton collisions at √s =13 TeV with the ATLAS, Physical Review D, 10.1103/PhysRevD.94.052002, 94, 5, 2016.09, [URL], A search for Higgs-boson pair production in the bbbb final state is carried out with 3.2 fb-1 of proton-proton collision data collected at s=13 TeV with the ATLAS detector. The data are consistent with the estimated background and are used to set upper limits on the production cross section of Higgs-boson pairs times branching ratio to bbbb for both nonresonant and resonant production. In the case of resonant production of Kaluza-Klein gravitons within the Randall-Sundrum model, upper limits in the 24 to 91 fb range are obtained for masses between 600 and 3000 GeV, at the 95% confidence level. The production cross section times branching ratio for nonresonant Higgs-boson pairs is also constrained to be less than 1.22 pb, at the 95% confidence level..
22. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, M. Adersberger, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, �kesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for heavy long-lived charged R-hadrons with the ATLAS detector in 3.2fb-1of proton-proton collision data at √s=13TeV, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 760, 647-665, 2016.09, A search for heavy long-lived charged R-hadronsis reported using a data sample corresponding to 3.2fb-1 of proton-proton collisions at √s=13TeVcollected by the ATLAS experiment at the Large Hadron Collider at CERN. The search is based on observables related to large ionisation losses and slow propagation velocities, which are signatures of heavy charged particles travelling significantly slower than the speed of light. No significant deviations from the expected background are observed. Upper limits at 95% confidence level are provided on the production cross section of long-lived R-hadronsin the mass range from 600GeVto 2000GeVand gluino, bottom and top squark masses are excluded up to 1580GeV, 805GeVand 890GeV, respectively..
23. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, M. Adersberger, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for heavy long-lived charged R-hadrons with the ATLAS detector in 3.2fb-1of proton-proton collision data at √s=13TeV, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.07.042, 760, 647-665, 2016.09, [URL], A search for heavy long-lived charged R-hadronsis reported using a data sample corresponding to 3.2fb-1 of proton-proton collisions at √s=13TeVcollected by the ATLAS experiment at the Large Hadron Collider at CERN. The search is based on observables related to large ionisation losses and slow propagation velocities, which are signatures of heavy charged particles travelling significantly slower than the speed of light. No significant deviations from the expected background are observed. Upper limits at 95% confidence level are provided on the production cross section of long-lived R-hadronsin the mass range from 600GeVto 2000GeVand gluino, bottom and top squark masses are excluded up to 1580GeV, 805GeVand 890GeV, respectively..
24. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, �kesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for TeV-scale gravity signatures in high-mass final states with leptons and jets with the ATLAS detector at √s = 13 TeV, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 760, 520-537, 2016.09, A search for physics beyond the Standard Model, in final states with at least one high transverse momentum charged lepton (electron or muon) and two additional high transverse momentum leptons or jets, is performed using 3.2 fb-1 of proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015 at √s = 13 TeV. The upper end of the distribution of the scalar sum of the transverse momenta of leptons and jets is sensitive to the production of high-mass objects. No excess of events beyond Standard Model predictions is observed. Exclusion limits are set for models of microscopic black holes with two to six extra dimensions..
25. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for TeV-scale gravity signatures in high-mass final states with leptons and jets with the ATLAS detector at √s = 13 TeV, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.07.030, 760, 520-537, 2016.09, [URL], A search for physics beyond the Standard Model, in final states with at least one high transverse momentum charged lepton (electron or muon) and two additional high transverse momentum leptons or jets, is performed using 3.2 fb-1 of proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015 at √s = 13 TeV. The upper end of the distribution of the scalar sum of the transverse momenta of leptons and jets is sensitive to the production of high-mass objects. No excess of events beyond Standard Model predictions is observed. Exclusion limits are set for models of microscopic black holes with two to six extra dimensions..
26. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for Higgs and Z Boson Decays to φγ with the ATLAS Detector, Physical Review Letters, 10.1103/PhysRevLett.117.111802, 117, 11, 2016.09, [URL], A search for the decays of the Higgs and Z bosons to a φ meson and a photon is performed with a pp collision data sample corresponding to an integrated luminosity of 2.7 fb-1 collected at s=13 TeV with the ATLAS detector at the LHC. No significant excess of events is observed above the background, and 95% confidence level upper limits on the branching fractions of the Higgs and Z boson decays to φγ of 1.4×10-3 and 8.3×10-6, respectively, are obtained..
27. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, R. Aben, M. Abolins, O. S. AbouZeid, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, G. Alimonti, L. Alio, J. Alison, S. P. Alkire, B. M.M. Allbrooke, P. P. Allport, A. Aloisio, A. Alonso, F. Alonso, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of total and differential W + W production cross sections in proton-proton collisions at √s=8 TeV with the ATLAS detector and limits on anomalous triple-gauge-boson couplings, Journal of High Energy Physics, 10.1007/JHEP09(2016)029, 2016, 9, 2016.09, [URL], The production of W boson pairs in proton-proton collisions at s=8 TeV is studied using data corresponding to 20.3 fb−1 of integrated luminosity collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The W bosons are reconstructed using their leptonic decays into electrons or muons and neutrinos. Events with reconstructed jets are not included in the candidate event sample. A total of 6636 WW candidate events are observed. Measurements are performed in fiducial regions closely approximating the detector acceptance. The integrated measurement is corrected for all acceptance effects and for the W branching fractions to leptons in order to obtain the total WW production cross section, which is found to be 71.1 ± 1.1(stat) − 5.0 + 5.7(syst) ± 1.4(lumi) pb. This agrees with the next-to-next-to-leading-order Standard Model prediction of 63. 2− 1.4 + 1.6(scale) ± 1.2(PDF) pb. Fiducial differential cross sections are measured as a function of each of six kinematic variables. The distribution of the transverse momentum of the leading lepton is used to set limits on anomalous triple-gauge-boson couplings.[Figure not available: see fulltext.].
28. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of jet activity in top quark events using the eμ final state with two b-tagged jets in pp collisions at √s=8 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP09(2016)074, 2016, 9, 2016.09, [URL], Measurements of the jet activity in tt¯ events produced in proton-proton collisions at s=8 TeV are presented, using 20.3 fb−1 of data collected by the ATLAS experiment at the Large Hadron Collider. The events were selected in the dilepton eμ decay channel with two identified b-jets. The numbers of additional jets for various jet transverse momentum (pT) thresholds, and the normalised differential cross-sections as a function of pT for the five highest-pT additional jets, were measured in the jet pseudo-rapidity range |η| < 4.5. The gap fraction, the fraction of events which do not contain an additional jet in a central rapidity region, was measured for several rapidity intervals as a function of the minimum pT of a single jet or the scalar sum of pT of all additional jets. These fractions were also measured in different intervals of the invariant mass of the eμbb¯ system. All measurements were corrected for detector effects, and found to be mostly well-described by predictions from next-to-leading-order and leading-order tt¯ event generators with appropriate parameter choices. The results can be used to further optimise the parameters used in such generators.[Figure not available: see fulltext.].
29. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Dark matter interpretations of ATLAS searches for the electroweak production of supersymmetric particles in √s=8 TeV proton-proton collisions, Journal of High Energy Physics, 10.1007/JHEP09(2016)175, 2016, 9, 2016.09, [URL], A selection of searches by the ATLAS experiment at the LHC for the electroweak production of SUSY particles are used to study their impact on the constraints on dark matter candidates. The searches use 20 fb−1 of proton-proton collision data at s=8 TeV. A likelihood-driven scan of a five-dimensional effective model focusing on the gaugino-higgsino and Higgs sector of the phenomenological minimal supersymmetric Standard Model is performed. This scan uses data from direct dark matter detection experiments, the relic dark matter density and precision flavour physics results. Further constraints from the ATLAS Higgs mass measurement and SUSY searches at LEP are also applied. A subset of models selected from this scan are used to assess the impact of the selected ATLAS searches in this five-dimensional parameter space. These ATLAS searches substantially impact those models for which the mass m(χ˜10) of the lightest neutralino is less than 65 GeV, excluding 86% of such models. The searches have limited impact on models with larger m(χ˜10) due to either heavy electroweakinos or compressed mass spectra where the mass splittings between the produced particles and the lightest supersymmetric particle is small.[Figure not available: see fulltext.].
30. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Charged-particle distributions at low transverse momentum in √s=13 TeV pp interactions measured with the ATLAS detector at the LHC, European Physical Journal C, 10.1140/epjc/s10052-016-4335-y, 76, 9, 2016.09, [URL], Measurements of distributions of charged particles produced in proton–proton collisions with a centre-of-mass energy of 13 TeV are presented. The data were recorded by the ATLAS detector at the LHC and correspond to an integrated luminosity of 151 μ b - 1. The particles are required to have a transverse momentum greater than 100 MeV and an absolute pseudorapidity less than 2.5. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the dependence of the mean transverse momentum on multiplicity are measured in events containing at least two charged particles satisfying the above kinematic criteria. The results are corrected for detector effects and compared to the predictions from several Monte Carlo event generators..
31. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, M. Abolins, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, The performance of the jet trigger for the ATLAS detector during 2011 data taking, European Physical Journal C, 10.1140/epjc/s10052-016-4325-0, 76, 10, 2016.10, [URL], The performance of the jet trigger for the ATLAS detector at the LHC during the 2011 data taking period is described. During 2011 the LHC provided proton–proton collisions with a centre-of-mass energy of 7 TeV and heavy ion collisions with a 2.76 TeV per nucleon–nucleon collision energy. The ATLAS trigger is a three level system designed to reduce the rate of events from the 40 MHz nominal maximum bunch crossing rate to the approximate 400 Hz which can be written to offline storage. The ATLAS jet trigger is the primary means for the online selection of events containing jets. Events are accepted by the trigger if they contain one or more jets above some transverse energy threshold. During 2011 data taking the jet trigger was fully efficient for jets with transverse energy above 25 GeV for triggers seeded randomly at Level 1. For triggers which require a jet to be identified at each of the three trigger levels, full efficiency is reached for offline jets with transverse energy above 60 GeV. Jets reconstructed in the final trigger level and corresponding to offline jets with transverse energy greater than 60 GeV, are reconstructed with a resolution in transverse energy with respect to offline jets, of better than 4 % in the central region and better than 2.5 % in the forward direction..
32. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for new phenomena in different-flavour high-mass dilepton final states in pp collisions at √s=13 Tev with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4385-1, 76, 10, 2016.10, [URL], A search is performed for a heavy particle decaying into different flavour dilepton pairs (eμ, eτ or μτ), using 3.2 fb- 1of proton–proton collision data at s=13 TeV collected in 2015 by the ATLAS detector at the Large Hadron Collider. No excess over the Standard Model prediction is observed. Limits at the 95 % credibility level are set on the mass of a Zboson with lepton-flavour-violating couplings at 3.0, 2.7 and 2.6 TeV, and on the mass of a supersymmetric τ sneutrino with R-parity-violating couplings at 2.3, 2.2 and 1.9 TeV, for eμ, eτ and μτ final states, respectively. The results are also interpreted as limits on the threshold mass for quantum black hole production..
33. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, �kesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for high-mass new phenomena in the dilepton final state using proton–proton collisions at s=13TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.08.055, 761, 372-392, 2016.10, [URL], A search is conducted for both resonant and non-resonant high-mass new phenomena in dielectron and dimuon final states. The search uses 3.2fb−1 of proton–proton collision data, collected at s=13TeV by the ATLAS experiment at the LHC in 2015. The dilepton invariant mass is used as the discriminating variable. No significant deviation from the Standard Model prediction is observed; therefore limits are set on the signal model parameters of interest at 95% credibility level. Upper limits are set on the cross-section times branching ratio for resonances decaying to dileptons, and the limits are converted into lower limits on the resonance mass, ranging between 2.74 TeV and 3.36 TeV, depending on the model. Lower limits on the ℓℓqq contact interaction scale are set between 16.7 TeV and 25.2 TeV, also depending on the model..
34. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, M. Abolins, O. S. AbouZeid, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, A. Alonso, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for gluinos in events with an isolated lepton, jets and missing transverse momentum at √s = 13 Te V with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4397-x, 76, 10, 2016.10, [URL], The results of a search for gluinos in final states with an isolated electron or muon, multiple jets and large missing transverse momentum using proton–proton collision data at a centre-of-mass energy of s=13TeV are presented. The dataset used was recorded in 2015 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 3.2 fb- 1. Six signal selections are defined that best exploit the signal characteristics. The data agree with the Standard Model background expectation in all six signal selections, and the largest deviation is a 2.1 standard deviation excess. The results are interpreted in a simplified model where pair-produced gluinos decay via the lightest chargino to the lightest neutralino. In this model, gluinos are excluded up to masses of approximately 1.6 Te V depending on the mass spectrum of the simplified model, thus surpassing the limits of previous searches..
35. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for bottom squark pair production in proton–proton collisions at √s=13 TeV with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4382-4, 76, 10, 2016.10, [URL], The result of a search for pair production of the supersymmetric partner of the Standard Model bottom quark (b~1) is reported. The search uses 3.2 fb- 1 of pp collisions at s=13 TeV collected by the ATLAS experiment at the Large Hadron Collider in 2015. Bottom squarks are searched for in events containing large missing transverse momentum and exactly two jets identified as originating from b-quarks. No excess above the expected Standard Model background yield is observed. Exclusion limits at 95 % confidence level on the mass of the bottom squark are derived in phenomenological supersymmetric R-parity-conserving models in which the b~1 is the lightest squark and is assumed to decay exclusively via b~1→bχ~10, where χ~10 is the lightest neutralino. The limits significantly extend previous results; bottom squark masses up to 800 (840) GeV are excluded for the χ~10 mass below 360 (100) GeV whilst differences in mass above 100 GeV between the b~1 and the χ~10 are excluded up to a b~1 mass of 500 GeV..
36. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, R. Aben, M. Abolins, O. S. AbouZeid, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, G. Alimonti, L. Alio, J. Alison, S. P. Alkire, B. M.M. Allbrooke, P. P. Allport, A. Aloisio, A. Alonso, F. Alonso, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurements of top-quark pair differential cross-sections in the lepton+jets channel in pp collisions at √s=8TeV using the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4366-4, 76, 10, 2016.10, [URL], Measurements of normalized differential cross-sections of top-quark pair production are presented as a function of the top-quark, tt¯ system and event-level kinematic observables in proton–proton collisions at a centre-of-mass energy of s=8TeV. The observables have been chosen to emphasize the tt¯ production process and to be sensitive to effects of initial- and final-state radiation, to the different parton distribution functions, and to non-resonant processes and higher-order corrections. The dataset corresponds to an integrated luminosity of 20.3 fb- 1, recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider. Events are selected in the lepton+jets channel, requiring exactly one charged lepton and at least four jets with at least two of the jets tagged as originating from a b-quark. The measured spectra are corrected for detector effects and are compared to several Monte Carlo simulations. The results are in fair agreement with the predictions over a wide kinematic range. Nevertheless, most generators predict a harder top-quark transverse momentum distribution at high values than what is observed in the data. Predictions beyond NLO accuracy improve the agreement with data at high top-quark transverse momenta. Using the current settings and parton distribution functions, the rapidity distributions are not well modelled by any generator under consideration. However, the level of agreement is improved when more recent sets of parton distribution functions are used..
37. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, A. Alonso, Kiyotomo Kawagoe, Measurement of the tt¯ production cross-section using eμ events with b-tagged jets in pp collisions at √s=13TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.08.019, 761, 136-157, 2016.10, [URL], This paper describes a measurement of the inclusive top quark pair production cross-section (σtt¯) with a data sample of 3.2fb−1 of proton–proton collisions at a centre-of-mass energy of s=13TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electron–muon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously σtt¯ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be: σtt¯=818±8(stat)±27(syst)±19(lumi)±12(beam) pb, where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented..
38. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, A. Alonso, Kiyotomo Kawagoe, Measurement of the top quark mass in the tt¯→dilepton channel from √s=8 TeV ATLAS data, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.08.042, 761, 350-371, 2016.10, [URL], The top quark mass is measured in the tt¯→dilepton channel (lepton=e,μ) using ATLAS data recorded in the year 2012 at the LHC. The data were taken at a proton–proton centre-of-mass energy of s=8 TeV and correspond to an integrated luminosity of about 20.2 fb−1. Exploiting the template method, and using the distribution of invariant masses of lepton–b-jet pairs, the top quark mass is measured to be mtop=172.99±0.41 (stat)±0.74 (syst) GeV, with a total uncertainty of 0.84 GeV. Finally, a combination with previous ATLAS mtop measurements from s=7 TeV data in the tt¯→dilepton and tt¯→lepton+jets channels results in mtop=172.84±0.34 (stat)±0.61 (syst) GeV, with a total uncertainty of 0.70 GeV..
39. M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo,, Measurement of the total cross section from elastic scattering in pp collisions at √s = 8 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.08.020, 761, 158-178, 2016.10, [URL], A measurement of the total pp cross section at the LHC at √s = 8 TeV is presented. An integrated luminosity of 500 μb-1 was accumulated in a special run with high-β beam optics to measure the differential elastic cross section as a function of the Mandelstam momentum transfer variable t. The measurement is performed with the ALFA sub-detector of ATLAS. Using a fit to the differential elastic cross section in the -t range from 0.014 GeV2 to 0.1 GeV2 to extrapolate t → 0, the total cross section, σtot (pp → X), is measured via the optical theorem to be σtot(pp→X) = 96.07±0.18 (stat.)±0.85 (exp.)± 0.31 (extr.) mb, where the first error is statistical, the second accounts for all experimental systematic uncertainties and the last is related to uncertainties in the extrapolation t → 0. In addition, the slope of the exponential function describing the elastic cross section at small t is determined to be B = 19.74±0.05 (stat.)±0.23 (syst.) GeV.-2..
40. M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo,, Measurement of the top quark mass in the tt̄ → Dilepton channel from √s=8 TeV ATLAS data, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.08.042, 761, 350-371, 2016.10, [URL], The top quark mass is measured in the tt̄ → dileptonchannel (lepton=e, µ) using ATLAS data recorded in the year 2012 at the LHC. The data were taken at a proton-proton centre-of-mass energy of √s=8 TeV and correspond to an integrated luminosity of about 20.2fb-1. Exploiting the template method, and using the distribution of invariant masses of lepton-b-jetpairs, the top quark mass is measured to be mtop=172.99 ±0.41 (stat) ±0.74 (syst) GeV, with a total uncertainty of 0.84 GeV. Finally, acombination with previous ATLAS mtop measurements from √s=7TeVdata in the tt̄ → dilepton and tt̄→lepton+jetschannels results in mtop=172.84 ±0.34 (stat) ±0.61 (syst) GeV, with a total uncertainty of 0.70 GeV..
41. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of the Inelastic Proton-Proton Cross Section at √s=13 TeV with the ATLAS Detector at the LHC, Physical Review Letters, 10.1103/PhysRevLett.117.182002, 117, 18, 2016.10, [URL], This Letter presents a measurement of the inelastic proton-proton cross section using 60 μb-1 of pp collisions at a center-of-mass energy s of 13 TeV with the ATLAS detector at the LHC. Inelastic interactions are selected using rings of plastic scintillators in the forward region (2.07<|η|<3.86) of the detector. A cross section of 68.1±1.4 mb is measured in the fiducial region ξ=MX2/s>10-6, where MX is the larger invariant mass of the two hadronic systems separated by the largest rapidity gap in the event. In this ξ range the scintillators are highly efficient. For diffractive events this corresponds to cases where at least one proton dissociates to a system with MX>13 GeV. The measured cross section is compared with a range of theoretical predictions. When extrapolated to the full phase space, a cross section of 78.1±2.9 mb is measured, consistent with the inelastic cross section increasing with center-of-mass energy..
42. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Study of hard double-parton scattering in four-jet events in pp collisions at √s=7 TeV with the ATLAS experiment, Journal of High Energy Physics, 10.1007/JHEP11(2016)110, 2016, 11, 2016.11, [URL], Inclusive four-jet events produced in proton-proton collisions at a centre-of-mass energy of s=7 TeV are analysed for the presence of hard double-parton scattering using data corresponding to an integrated luminosity of 37.3 pb−1, collected with the ATLAS detector at the LHC. The contribution of hard double-parton scattering to the production of four-jet events is extracted using an artificial neural network, assuming that hard double-parton scattering can be approximated by an uncorrelated overlaying of dijet events. For events containing at least four jets with transverse momentum pT ≥ 20 GeV and pseudorapidity |η| ≤ 4.4, and at least one having pT ≥ 42.5 GeV, the contribution of hard double-parton scattering is estimated to be fDPS = 0.092− 0.011 + 0.005(stat.)− 0.037 + 0.033(syst.). After combining this measurement with those of the inclusive dijet and four-jet cross-sections in the appropriate phase space regions, the effective cross-section, σeff , was determined to be σeff = 14. 9− 1.0 + 1.2(stat.)− 3.8 + 5.1(syst.) mb. This result is consistent within the quoted uncertainties with previous measurements of σeff , performed at centre-of-mass energies between 63 GeV and 8 TeV using various final states, and it corresponds to 21− 6 + 7 % of the total inelastic cross-section measured at s=7 TeV. The distributions of the observables sensitive to the contribution of hard double-parton scattering, corrected for detector effects, are also provided.[Figure not available: see fulltext.].
43. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for the Standard Model Higgs boson produced by vector-boson fusion and decaying to bottom quarks in √s=8 TeV pp collisions with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP11(2016)112, 2016, 11, 2016.11, [URL], A search with the ATLAS detector is presented for the Standard Model Higgs boson produced by vector-boson fusion and decaying to a pair of bottom quarks, using 20.2 fb−1 of LHC proton-proton collision data at s=8 TeV. The signal is searched for as a resonance in the invariant mass distribution of a pair of jets containing b-hadrons in vector-boson-fusion candidate events. The yield is measured to be −0.8 ± 2.3 times the Standard Model cross-section for a Higgs boson mass of 125 GeV. The upper limit on the cross-section times the branching ratio is found to be 4.4 times the Standard Model cross-section at the 95% confidence level, consistent with the expected limit value of 5.4 (5.7) in the background-only (Standard Model production) hypothesis.[Figure not available: see fulltext.].
44. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for the Higgs boson produced in association with a W boson and decaying to four b-quarks via two spin-zero particles in pp collisions at 13 TeV with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4418-9, 76, 11, 2016.11, [URL], This paper presents a dedicated search for exotic decays of the Higgs boson to a pair of new spin-zero particles, H→ aa, where the particle a decays to b-quarks and has a mass in the range of 20–60 GeV. The search is performed in events where the Higgs boson is produced in association with a W boson, giving rise to a signature of a lepton (electron or muon), missing transverse momentum, and multiple jets from b-quark decays. The analysis is based on the full dataset of pp collisions at s=13TeV recorded in 2015 by the ATLAS detector at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 3.2 fb-1. No significant excess of events above the Standard Model prediction is observed, and a 95% confidence-level upper limit is derived for the product of the production cross section for pp→ WH times the branching ratio for the decay H→ aa→ 4 b. The upper limit ranges from 6.2 pb for an a-boson mass ma=20GeV to 1.5 pb for ma=60GeV..
45. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abou Zeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, �kesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for new resonances in events with one lepton and missing transverse momentum in pp collisions at √s = 13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 762, 334-352, 2016.11, A search for W' bosons in events with one lepton (electron or muon) and missing transverse momentum is presented. The search uses 3.2 fb-1 of ppcollision data collected at √s = 13 TeV TeV by the ATLAS experiment at the LHC in 2015. The transverse mass distribution is examined and no significant excess of events above the level expected from Standard Model processes is observed. Upper limits on the W' boson cross-section times branching ratio to leptons are set as a function of the W' mass. Within the Sequential Standard Model W' masses below 4.07 TeV are excluded at the 95% confidence level. This extends the limit set using LHC data at √s = 8 TeV by around 800 GeV..
46. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abou Zeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for new resonances in events with one lepton and missing transverse momentum in pp collisions at √s = 13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.09.040, 762, 334-352, 2016.11, [URL], A search for W' bosons in events with one lepton (electron or muon) and missing transverse momentum is presented. The search uses 3.2 fb-1 of ppcollision data collected at √s = 13 TeV TeV by the ATLAS experiment at the LHC in 2015. The transverse mass distribution is examined and no significant excess of events above the level expected from Standard Model processes is observed. Upper limits on the W' boson cross-section times branching ratio to leptons are set as a function of the W' mass. Within the Sequential Standard Model W' masses below 4.07 TeV are excluded at the 95% confidence level. This extends the limit set using LHC data at √s = 8 TeV by around 800 GeV..
47. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for minimal supersymmetric standard model Higgs Bosons H / A and for a Z boson in the ττ final state produced in pp collisions at √s=13 TeV with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4400-6, 76, 11, 2016.11, [URL], A search for neutral Higgs bosons of the minimal supersymmetric standard model (MSSM) and for a heavneutral Z boson is performed using a data sample corresponding to an integrated luminosity of 3.2 fb- 1 from proton–proton collisions at s=13 TeV recorded by the ATLAS detector at the LHC. The heavy resonance is assumed to decay to a τ+τ- pair with at least one τ lepton decaying to final states with hadrons and a neutrino. The search is performed in the mass range of 0.2–1.2 TeV for the MSSM neutral Higgs bosons and 0.5–2.5 TeV for the heavy neutral Z boson. The data are in good agreement with the background predicted by the Standard Model. The results are interpreted in MSSM and Z benchmark scenarios. The most stringent constraints on the MSSM mA–tan β space exclude at 95 % confidence level (CL) tan β> 7.6 for mA= 200 GeV in the mhmod+ MSSM scenario. For the Sequential Standard Model, a ZSSM′ mass up to 1.90 TeV is excluded at 95 % CL and masses up to 1.82–2.17 TeV are excluded for a ZSFM′ of the strong flavour model..
48. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, R. Aben, M. Abolins, O. S. AbouZeid, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, G. Alimonti, L. Alio, J. Alison, S. P. Alkire, B. M.M. Allbrooke, P. P. Allport, A. Aloisio, A. Alonso, F. Alonso, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Performance of pile-up mitigation techniques for jets in pp collisions at √s=8 TeV using the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4395-z, 76, 11, 2016.11, [URL], The large rate of multiple simultaneous proton–proton interactions, or pile-up, generated by the Large Hadron Collider in Run 1 required the development of many new techniques to mitigate the adverse effects of these conditions. This paper describes the methods employed in the ATLAS experiment to correct for the impact of pile-up on jet energy and jet shapes, and for the presence of spurious additional jets, with a primary focus on the large 20.3 fb- 1data sample collected at a centre-of-mass energy of s=8TeV. The energy correction techniques that incorporate sophisticated estimates of the average pile-up energy density and tracking information are presented. Jet-to-vertex association techniques are discussed and projections of performance for the future are considered. Lastly, the extension of these techniques to mitigate the effect of pile-up on jet shapes using subtraction and grooming procedures is presented..
49. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of top quark pair differential cross sections in the dilepton channel in pp collisions at √s =7 and 8 TeV with ATLAS, Physical Review D, 10.1103/PhysRevD.94.092003, 94, 9, 2016.11, [URL], Measurements of normalized differential cross sections of top quark pair (tt production are presented as a function of the mass, the transverse momentum and the rapidity of the tt system in proton-proton collisions at center-of-mass energies of s=7 and 8 TeV. The data set corresponds to an integrated luminosity of 4.6 fb-1 at 7 TeV and 20.2 fb-1 at 8 TeV, recorded with the ATLAS detector at the Large Hadron Collider. Events with top quark pair signatures are selected in the dilepton final state, requiring exactly two charged leptons and at least two jets with at least one of the jets identified as likely to contain a b hadron. The measured distributions are corrected for detector effects and selection efficiency to cross sections at the parton level. The differential cross sections are compared with different Monte Carlo generators and theoretical calculations of tt production. The results are consistent with the majority of predictions in a wide kinematic range..
50. M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, A. Alonso, Kiyotomo Kawagoe, Measurement of the W±Z boson pair-production cross section in pp collisions at s=13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.08.052, 762, 1-22, 2016.11, [URL], The production of W±Z events in proton–proton collisions at a centre-of-mass energy of 13 TeV is measured with the ATLAS detector at the LHC. The collected data correspond to an integrated luminosity of 3.2 fb−1. The W±Z candidates are reconstructed using leptonic decays of the gauge bosons into electrons or muons. The measured inclusive cross section in the detector fiducial region for leptonic decay modes is σW±Z→ℓνℓℓ fid.=63.2±3.2(stat.)±2.6(sys.)±1.5(lumi.) fb. In comparison, the next-to-leading-order Standard Model prediction is 53.4−2.8 +3.6 fb. The extrapolation of the measurement from the fiducial to the total phase space yields σW±Z tot.=50.6±2.6(stat.)±2.0(sys.)±0.9(th.)±1.2(lumi.) pb, in agreement with a recent next-to-next-to-leading-order calculation of 48.2−1.0 +1.1 pb. The cross section as a function of jet multiplicity is also measured, together with the charge-dependent W+Z and WZ cross sections and their ratio..
51. M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, A measurement of material in the ATLAS tracker using secondary hadronic interactions in 7TeV pp collisions, Journal of Instrumentation, 10.1088/1748-0221/11/11/P11020, 11, 11, 2016.11, [URL], Knowledge of the material in the ATLAS inner tracking detector is crucial in understanding the reconstruction of charged-particle tracks, the performance of algorithms that identify jets containing b-hadrons and is also essential to reduce background in searches for exotic particles that can decay within the inner detector volume. Interactions of primary hadrons produced in pp collisions with the material in the inner detector are used to map the location and amount of this material. The hadronic interactions of primary particles may result in secondary vertices, which in this analysis are reconstructed by an inclusive vertex-finding algorithm. Data were collected using minimum-bias triggers by the ATLAS detector operating at the LHC during 2010 at centre-of-mass energy √s = 7TeV, and correspond to an integrated luminosity of 19nb-1. Kinematic properties of these secondary vertices are used to study the validity of the modelling of hadronic interactions in simulation. Secondary-vertex yields are compared between data and simulation over a volume of about 0.7 m3 around the interaction point, and agreement is found within overall uncertainties..
52. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, �kesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Transverse momentum, rapidity, and centrality dependence of inclusive charged-particle production in sNN=5.02 TeV p + Pb collisions measured by the ATLAS experiment, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.10.053, 763, 313-336, 2016.12, [URL], Measurements of the per-event charged-particle yield as a function of the charged-particle transverse momentum and rapidity are performed using p+Pb collision data collected by the ATLAS experiment at the LHC at a centre-of-mass energy of sNN=5.02TeV. Charged particles are reconstructed over pseudorapidity |η|<2.3 and transverse momentum between 0.1 GeV and 22 GeV in a dataset corresponding to an integrated luminosity of 1 μb−1. The results are presented in the form of charged-particle nuclear modification factors, where the p+Pb charged-particle multiplicities are compared between central and peripheral p+Pb collisions as well as to charged-particle cross sections measured in pp collisions. The p+Pb collision centrality is characterized by the total transverse energy measured in −4.9<η<−3.1, which is in the direction of the outgoing lead beam. Three different estimations of the number of nucleons participating in the p+Pb collision are carried out using the Glauber model and two Glauber–Gribov colour-fluctuation extensions to the Glauber model. The values of the nuclear modification factors are found to vary significantly as a function of rapidity and transverse momentum. A broad peak is observed for all centralities and rapidities in the nuclear modification factors for charged-particle transverse momentum values around 3 GeV. The magnitude of the peak increases for more central collisions as well as rapidity ranges closer to the direction of the outgoing lead nucleus..
53. , G. Aad, B. Abbott, O. Abdinov, J. Abdallah, B. Abeloos, R. Aben, M. Abolins, R. Aben, M. Abolins, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Test of CP invariance in vector-boson fusion production of the Higgs boson using the Optimal Observable method in the ditau decay channel with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4499-5, 76, 12, 2016.12, [URL], A test of CP invariance in Higgs boson production via vector-boson fusion using the method of the Optimal Observable is presented. The analysis exploits the decay mode of the Higgs boson into a pair of τ leptons and is based on 20.3 fb - 1 of proton–proton collision data at s = 8 TeV collected by the ATLAS experiment at the LHC. Contributions from CP-violating interactions between the Higgs boson and electroweak gauge bosons are described in an effective field theory framework, in which the strength of CP violation is governed by a single parameter d~. The mean values and distributions of CP-odd observables agree with the expectation in the Standard Model and show no sign of CP violation. The CP-mixing parameter d~ is constrained to the interval (- 0.11 , 0.05) at 68% confidence level, consistent with the Standard Model expectation of d~ = 0..
54. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for squarks and gluinos in events with hadronically decaying tau leptons, jets and missing transverse momentum in proton–proton collisions at √s=13 TeV recorded with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4481-2, 76, 12, 2016.12, [URL], A search for supersymmetry in events with large missing transverse momentum, jets, and at least one hadronically decaying tau lepton has been performed using 3.2 fb-1 of proton–proton collision data at s=13TeV recorded by the ATLAS detector at the Large Hadron Collider in 2015. Two exclusive final states are considered, with either exactly one or at least two tau leptons. No excess over the Standard Model prediction is observed in the data. Results are interpreted in the context of gauge-mediated supersymmetry breaking and a simplified model of gluino pair production with tau-rich cascade decays, substantially improving on previous limits. In the GMSB model considered, supersymmetry-breaking scale (Λ) values below 92TeV are excluded at the 95% confidence level, corresponding to gluino masses below 2000GeV. For large values of tan β, values of Λ up to 107TeV and gluino masses up to 2300GeV are excluded. In the simplified model, gluino masses are excluded up to 1570GeV for neutralino masses around 100GeV. Neutralino masses below 700GeV are excluded for all gluino masses between 800 and 1500GeV, while the strongest exclusion of 750GeV is achieved for gluino masses around 1450GeV..
55. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for dark matter produced in association with a hadronically decaying vector boson in pp collisions at √s=13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.10.042, 763, 251-268, 2016.12, [URL], A search is presented for dark matter produced in association with a hadronically decaying W or Z boson using 3.2 fb−1 of pp collisions at s=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet compatible with a W or Z boson and with large missing transverse momentum are analysed. The data are consistent with the Standard Model predictions and are interpreted in terms of both an effective field theory and a simplified model containing dark matter..
56. M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. AlconadaVerzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, A. Alonso, F. Alonso, C. Alpigiani, A. A. Alshehri, M. Alstaty, B. AlvarezGonzalez, Álvarez Piqueras D., M. G. Alviggi, B. T. Amadio, K. Amako, Y. AmaralCoutinho, C. Amelung, D. Amidei, S. P. Amor Dos Santos, A. Amorim, S. Amoroso, G. Amundsen, C. Anastopoulos, L. S. Ancu, N. Andari, T. Andeen, C. F. Anders, G. Anders, J. K. Anders, K. J. 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Solovyev, P. Sommer, H. Son, H. Y. Song, A. Sood, A. Sopczak, V. Sopko, V. Sorin, D. Sosa, C. L. Sotiropoulou, R. Soualah, A. M. Soukharev, D. South, B. C. Sowden, S. Spagnolo, M. Spalla, M. Spangenberg, F. Spanò, D. Sperlich, F. Spettel, R. Spighi, G. Spigo, L. A. Spiller, M. Spousta, R. D. St.Denis, A. Stabile, R. Stamen, S. Stamm, E. Stanecka, R. W. Stanek, C. Stanescu, M. Stanescu-Bellu, M. M. Stanitzki, S. Stapnes, E. A. Starchenko, G. H. Stark, J. Stark, P. Staroba, P. Starovoitov, S. Stärz, R. Staszewski, P. Steinberg, B. Stelzer, H. J. Stelzer, O. Stelzer-Chilton, H. Stenzel, G. A. Stewart, J. A. Stillings, M. C. Stockton, M. Stoebe, G. Stoicea, P. Stolte, S. Stonjek, A. R. Stradling, A. Straessner, M. E. Stramaglia, J. Strandberg, S. Strandberg, A. Strandlie, M. Strauss, P. Strizenec, R. Ströhmer, D. M. Strom, R. Stroynowski, A. Strubig, S. A. Stucci, B. Stugu, N. A. Styles, D. Su, J. Su, S. Suchek, Y. Sugaya, M. Suk, V. V. Sulin, S. Sultansoy, T. Sumida, S. Sun, X. Sun, J. 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Valero, L. Valery, S. Valkar, J. A. Valls Ferrer, W. Van Den Wollenberg, P. C. Van Der Deijl, H. van der Graaf, N. van Eldik, P. van Gemmeren, J. Van Nieuwkoop, I. van Vulpen, M. C. van Woerden, M. Vanadia, W. Vandelli, R. Vanguri, A. Vaniachine, P. Vankov, G. Vardanyan, R. Vari, E. W. Varnes, T. Varol, D. Varouchas, A. Vartapetian, K. E. Varvell, J. G. Vasquez, G. A. Vasquez, F. Vazeille, T. Vazquez Schroeder, J. Veatch, V. Veeraraghavan, L. M. Veloce, F. Veloso, S. Veneziano, A. Ventura, M. Venturi, N. Venturi, A. Venturini, V. Vercesi, M. Verducci, W. Verkerke, J. C. Vermeulen, A. Vest, M. C. Vetterli, O. Viazlo, I. Vichou, T. Vickey, O. E. Vickey Boeriu, G. H.A. Viehhauser, S. Viel, L. Vigani, M. Villa, M. Villaplana Perez, E. Vilucchi, M. G. Vincter, V. B. Vinogradov, C. Vittori, I. Vivarelli, S. Vlachos, M. Vlasak, M. Vogel, P. Vokac, G. Volpi, M. Volpi, H. von der Schmitt, E. von Toerne, V. Vorobel, K. Vorobev, M. Vos, R. Voss, J. H. Vossebeld, N. Vranjes, M. Vranjes Milosavljevic, V. Vrba, M. Vreeswijk, R. Vuillermet, I. Vukotic, Z. Vykydal, P. Wagner, W. Wagner, H. Wahlberg, S. Wahrmund, J. Wakabayashi, J. Walder, R. Walker, W. Walkowiak, V. Wallangen, C. Wang, C. Wang, F. Wang, H. Wang, H. Wang, J. Wang, J. Wang, K. Wang, R. Wang, S. M. Wang, T. Wang, T. Wang, W. Wang, X. Wang, C. Wanotayaroj, A. Warburton, C. P. Ward, D. R. Wardrope, A. Washbrook, P. M. Watkins, A. T. Watson, M. F. Watson, G. Watts, S. Watts, B. M. Waugh, S. Webb, M. S. Weber, S. W. Weber, S. A. Weber, J. S. Webster, A. R. Weidberg, B. Weinert, J. Weingarten, C. Weiser, H. Weits, P. S. Wells, T. Wenaus, T. Wengler, S. Wenig, N. Wermes, M. Werner, M. D. Werner, P. Werner, M. Wessels, J. Wetter, K. Whalen, N. L. Whallon, A. M. Wharton, A. White, M. J. White, R. White, D. Whiteson, F. J. Wickens, W. Wiedenmann, M. Wielers, C. Wiglesworth, L. A.M. Wiik-Fuchs, A. Wildauer, F. Wilk, H. G. Wilkens, H. H. Williams, S. Williams, C. Willis, S. Willocq, J. A. Wilson, I. Wingerter-Seez, F. Winklmeier, O. J. Winston, B. T. Winter, M. Wittgen, J. Wittkowski, T. M.H. Wolf, M. W. Wolter, H. Wolters, S. D. Worm, B. K. Wosiek, J. Wotschack, M. J. Woudstra, K. W. Wozniak, M. Wu, M. Wu, S. L. Wu, X. Wu, Y. Wu, T. R. Wyatt, B. M. Wynne, S. Xella, D. Xu, L. Xu, B. Yabsley, S. Yacoob, D. Yamaguchi, Y. Yamaguchi, A. Yamamoto, S. Yamamoto, T. Yamanaka, K. Yamauchi, Y. Yamazaki, Z. Yan, H. Yang, H. Yang, Y. Yang, Z. Yang, W. M. Yao, Y. C. Yap, Y. Yasu, E. Yatsenko, K. H. Yau Wong, J. Ye, S. Ye, I. Yeletskikh, A. L. Yen, E. Yildirim, K. Yorita, R. Yoshida, K. Yoshihara, C. Young, C. J.S. Young, S. Youssef, D. R. Yu, J. Yu, J. M. Yu, J. Yu, L. Yuan, S. P.Y. Yuen, I. Yusuff, B. Zabinski, R. Zaidan, A. M. Zaitsev, N. Zakharchuk, J. Zalieckas, A. Zaman, S. Zambito, L. Zanello, D. Zanzi, C. Zeitnitz, M. Zeman, A. Zemla, J. C. Zeng, Q. Zeng, K. Zengel, O. Zenin, Ženiš T., D. Zerwas, D. Zhang, F. Zhang, G. Zhang, H. Zhang, J. Zhang, L. Zhang, R. Zhang, R. Zhang, X. Zhang, Z. Zhang, X. Zhao, Y. Zhao, Z. Zhao, A. Zhemchugov, J. Zhong, B. Zhou, C. Zhou, L. Zhou, L. Zhou, M. Zhou, N. Zhou, C. G. Zhu, H. Zhu, J. Zhu, Y. Zhu, X. Zhuang, K. Zhukov, A. Zibell, D. Zieminska, N. I. Zimine, C. Zimmermann, S. Zimmermann, Z. Zinonos, M. Zinser, M. Ziolkowski, Živković L., G. Zobernig, A. Zoccoli, M. zur Nedden, L. Zwalinski,, Search for dark matter produced in association with a hadronically decaying vector boson in pp collisions at √s = 13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.10.042, 763, 251-268, 2016.12, [URL], A search is presented for dark matter produced in association with a hadronically decaying W or Z boson using 3.2 fb-1 of pp collisions at √ s = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet compatible with a W or Z boson and with large missing transverse momentum are analysed. The data are consistent with the Standard Model predictions and are interpreted in terms of both an effective field theory and a simplified model containing dark matter..
57. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of the photon identification efficiencies with the ATLAS detector using LHC Run-1 data, European Physical Journal C, 10.1140/epjc/s10052-016-4507-9, 76, 12, 2016.12, [URL], The algorithms used by the ATLAS Collaboration to reconstruct and identify prompt photons are described. Measurements of the photon identification efficiencies are reported, using 4.9 fb- 1 of pp collision data collected at the LHC at s=7 TeV and 20.3 fb- 1 at s=8 TeV. The efficiencies are measured separately for converted and unconverted photons, in four different pseudorapidity regions, for transverse momenta between 10 GeV and 1.5 TeV. The results from the combination of three data-driven techniques are compared to the predictions from a simulation of the detector response, after correcting the electromagnetic shower momenta in the simulation for the average differences observed with respect to data. Data-to-simulation efficiency ratios used as correction factors in physics measurements are determined to account for the small residual efficiency differences. These factors are measured with uncertainties between 0.5% and 10% in 7 TeV data and between 0.5% and 5.6% in 8 TeV data, depending on the photon transverse momentum and pseudorapidity..
58. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of the bb¯ dijet cross section in pp collisions at √s=7 TeV with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4521-y, 76, 12, 2016.12, [URL], The dijet production cross section for jets containing a b-hadron (b-jets) has been measured in proton–proton collisions with a centre-of-mass energy of s=7 TeV, using the ATLAS detector at the LHC. The data used correspond to an integrated luminosity of 4.2fb-1. The cross section is measured for events with two identified b-jets with a transverse momentum pT> 20 GeV and a minimum separation in the η–ϕ plane of Δ R= 0.4. At least one of the jets in the event is required to have pT> 270 GeV. The cross section is measured differentially as a function of dijet invariant mass, dijet transverse momentum, boost of the dijet system, and the rapidity difference, azimuthal angle and angular distance between the b-jets. The results are compared to different predictions of leading order and next-to-leading order perturbative quantum chromodynamics matrix elements supplemented with models for parton-showers and hadronization..
59. M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, �kesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. AlconadaVerzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of W+W-production in association with one jet in proton-proton collisions at √s = 8 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.10.014, 763, 114-133, 2016.12, [URL], The production of Wboson pairs in association with one jet in pp collisions at √s = 8 TeV is studied using data corresponding to an integrated luminosity of 20.3 fb-1collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The cross section is measured in a fiducial phase-space region defined by the presence of exactly one electron and one muon, missing transverse momentum and exactly one jet with a transverse momentum above 25 GeV and a pseudorapidity of |η| <4.5. The leptons are required to have opposite electric charge and to pass transverse momentum and pseudorapidity requirements. The fiducial cross section is found to be σWW fid,1-jet= 136 � 6 (stat)� 14 (syst)� 3 (lumi) fb. In combination with a previous measurement restricted to leptonic final states with no associated jets, the fiducial cross section of WW production with zero or one jet is measured to be σWW fid,≤1-jet= 511 �9 (stat)�26 (syst)�10 (lumi)fb. The ratio of fiducial cross sections in final states with one and zero jets is determined to be 0.36 �0.05. Finally, a total cross section extrapolated from the fiducial measurement of WW production with zero or one associated jet is reported. The measurements are compared to theoretical predictions and found in good agreement..
60. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Luminosity determination in pp collisions at √s = 8 TeV using the ATLAS detector at the LHC, European Physical Journal C, 10.1140/epjc/s10052-016-4466-1, 76, 12, 2016.12, [URL], The luminosity determination for the ATLAS detector at the LHC during pp collisions at s= 8 TeV in 2012 is presented. The evaluation of the luminosity scale is performed using several luminometers, and comparisons between these luminosity detectors are made to assess the accuracy, consistency and long-term stability of the results. A luminosity uncertainty of δL/ L= ± 1.9 % is obtained for the 22.7fb-1 of pp collision data delivered to ATLAS at s= 8 TeV in 2012..
61. G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, M. Abolins, O. S. AbouZeid, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, G. Alimonti, L. Alio, J. Alison, S. P. Alkire, B. M.M. Allbrooke, P. P. Allport, A. Aloisio, A. Alonso, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, ATLAS Collaboration, Nuclear Physics A, 10.1016/S0375-9474(16)30232-9, 956, 922-944, 2016.12, [URL].
62. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, �kesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for heavy resonances decaying to a Z boson and a photon in pp collisions at s=13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.11.005, 764, 11-30, 2017.01, [URL], This Letter presents a search for new resonances with mass larger than 250 GeV, decaying to a Z boson and a photon. The dataset consists of an integrated luminosity of 3.2 fb−1 of pp collisions collected at s=13 TeV with the ATLAS detector at the Large Hadron Collider. The Z bosons are identified through their decays either to charged, light, lepton pairs (e+e, μ+μ) or to hadrons. The data are found to be consistent with the expected background in the whole mass range investigated and upper limits are set on the production cross section times decay branching ratio to Zγ of a narrow scalar boson with mass between 250 GeV and 2.75 TeV..
63. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurements of ψ(2S) and X(3872) → J/ψπ + π production in pp collisions at √s=8 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP01(2017)117, 2017, 1, 2017.01, [URL], Differential cross sections are presented for the prompt and non-prompt production of the hidden-charm states X(3872) and ψ(2S), in the decay mode J/ψπ+π, measured using 11.4 fb−1 of pp collisions at s=8 TeV by the ATLAS detector at the LHC. The ratio of cross-sections X(3872)/ψ(2S) is also given, separately for prompt and non-prompt components, as well as the non-prompt fractions of X(3872) and ψ(2S). Assuming independent single effective lifetimes for non-prompt X(3872) and ψ(2S) production gives RB=ℬ(B→X(3872)+any)ℬ(X(3872)→J/ψπ+π−)/ℬ(B→ψ(2S)+any)ℬ(ψ(2S)→J/ψπ+π−)=(3.95±0.32(stat)±0.08(sys))×10−2 separating short- and long-lived contributions, assuming that the short-lived component is due to Bc decays, gives RB = (3.57 ± 0.33(stat) ± 0.11(sys)) × 10−2, with the fraction of non-prompt X(3872) produced via Bc decays for pT(X(3872)) > 10 GeV being (25 ± 13(stat) ± 2(sys) ± 5(spin))%. The distributions of the dipion invariant mass in the X(3872) and ψ(2S) decays are also measured and compared to theoretical predictions.[Figure not available: see fulltext.].
64. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of the tt¯Z and tt¯W production cross sections in multilepton final states using 3.2 fb -1 of pp collisions at √s = 13 TeV with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4574-y, 77, 1, 2017.01, [URL], A measurement of the tt¯ Z and tt¯ W production cross sections in final states with either two same-charge muons, or three or four leptons (electrons or muons) is presented. The analysis uses a data sample of proton–proton collisions at s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015, corresponding to a total integrated luminosity of 3.2 fb- 1. The inclusive cross sections are extracted using likelihood fits to signal and control regions, resulting in σt Z= 0.9 ± 0.3 pb and σt W= 1.5 ± 0.8 pb, in agreement with the Standard Model predictions..
65. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of the ZZ production cross section in proton-proton collisions at √s=8 TeV using the ZZ → ℓ+′−′+ and ZZ→ ℓ+νν¯ decay channels with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP01(2017)099, 2017, 1, 2017.01, [URL], A measurement of the ZZ production cross section in the ℓ+′ −′ + and ℓ+νν¯ channels (ℓ = e, μ) in proton-proton collisions at s=8TeV at the Large Hadron Collider at CERN, using data corresponding to an integrated luminosity of 20.3 fb−1 collected by the ATLAS experiment in 2012 is presented. The fiducial cross sections for ZZ → ℓ+′ −′ + and ZZ→ ℓ+νν¯ are measured in selected phase-space regions. The total cross section for ZZ events produced with both Z bosons in the mass range 66 to 116 GeV is measured from the combination of the two channels to be 7.3 ± 0.4(stat) ± 0.3(syst)− 0.1 − 0.2(lumi) pb, which is consistent with the Standard Model prediction of 6. 6− 0.6 + 0.7 pb. The differential cross sections in bins of various kinematic variables are presented. The differential event yield as a function of the transverse momentum of the leading Z boson is used to set limits on anomalous neutral triple gauge boson couplings in ZZ production.[Figure not available: see fulltext.].
66. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of W±W± vector-boson scattering and limits on anomalous quartic gauge couplings with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.96.012007, 96, 1, 2017.01, [URL], This paper presents the extended results of measurements of W±W±jj production and limits on anomalous quartic gauge couplings using 20.3 fb-1 of proton-proton collision data at s=8 TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with two leptons (e or μ) with the same electric charge and at least two jets are analyzed. Production cross sections are determined in two fiducial regions, with different sensitivities to the electroweak and strong production mechanisms. An additional fiducial region, particularly sensitive to anomalous quartic gauge coupling parameters α4 and α5, is introduced, which allows more stringent limits on these parameters compared to the previous ATLAS measurement..
67. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, A measurement of the calorimeter response to single hadrons and determination of the jet energy scale uncertainty using LHC Run-1 pp-collision data with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-016-4580-0, 77, 1, 2017.01, [URL], A measurement of the calorimeter response to isolated charged hadrons in the ATLAS detector at the LHC is presented. This measurement is performed with 3.2 nb- 1 of proton–proton collision data at s=7 TeV from 2010 and 0.1 nb- 1 of data at s=8 TeV from 2012. A number of aspects of the calorimeter response to isolated hadrons are explored. After accounting for energy deposited by neutral particles, there is a 5% discrepancy in the modelling, using various sets of Geant4 hadronic physics models, of the calorimeter response to isolated charged hadrons in the central calorimeter region. The description of the response to anti-protons at low momenta is found to be improved with respect to previous analyses. The electromagnetic and hadronic calorimeters are also examined separately, and the detector simulation is found to describe the response in the hadronic calorimeter well. The jet energy scale uncertainty and correlations in scale between jets of different momenta and pseudorapidity are derived based on these studies. The uncertainty is 2–5% for jets with transverse momenta above 2 TeV, where this method provides the jet energy scale uncertainty for ATLAS..
68. M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, �kesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for new resonances decaying to a W or Z boson and a Higgs boson in the ℓ+bb�, ℓνbb�, and νν�bb� channels with pp collisions at s=13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.11.045, 765, 32-52, 2017.02, [URL], A search is presented for new resonances decaying to a W or Z boson and a Higgs boson in the ℓ+bb�, ℓνbb�, and νν�bb� channels in pp collisions at s=13 TeV with the ATLAS detector at the Large Hadron Collider using a total integrated luminosity of 3.2 fb−1. The search is conducted by looking for a localized excess in the WH/ZH invariant or transverse mass distribution. No significant excess is observed, and the results are interpreted in terms of constraints on a simplified model based on a phenomenological Lagrangian of heavy vector triplets..
69. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, M. Abolins, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for lepton-flavour-violating decays of the Higgs and Z bosons with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-4624-0, 77, 2, 2017.02, [URL], Direct searches for lepton flavour violation in decays of the Higgs and Z bosons with the ATLAS detector at the LHC are presented. The following three decays are considered: H→ eτ, H→ μτ, and Z→ μτ. The searches are based on the data sample of proton–proton collisions collected by the ATLAS detector corresponding to an integrated luminosity of 20.3 fb - 1 at a centre-of-mass energy of s=8 TeV. No significant excess is observed, and upper limits on the lepton-flavour-violating branching ratios are set at the 95% confidence level: Br(H→ eτ) < 1.04 % , Br(H→ μτ) < 1.43 % , and Br(Z→ μτ) < 1.69 × 10 - 5..
70. M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo,, Search for dark matter in association with a Higgs boson decaying to b-quarks in pp collisions at s=13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.11.035, 765, 11-31, 2017.02, [URL], A search for dark matter pair production in association with a Higgs boson decaying to a pair of bottom quarks is presented, using 3.2 fb−1of pp collisions at a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the LHC. The decay of the Higgs boson is reconstructed as a high-momentum bb¯ system with either a pair of small-radius jets, or a single large-radius jet with substructure. The observed data are found to be consistent with the expected backgrounds. Results are interpreted using a simplified model with a Zgauge boson mediating the interaction between dark matter and the Standard Model as well as a two-Higgs-doublet model containing an additional Zboson which decays to a Standard Model Higgs boson and a new pseudoscalar Higgs boson, the latter decaying into a pair of dark matter particles..
71. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for anomalous electroweak production of WW /WZ in association with a high-mass dijet system in pp collisions at s =8 TeV with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.95.032001, 95, 3, 2017.02, [URL], A search is presented for anomalous quartic gauge boson couplings in vector-boson scattering. The data for the analysis correspond to 20.2 fb-1 of s=8 TeV pp collisions and were collected in 1972 by the ATLAS experiment at the Large Hadron Collider. The search looks for the production of WW or WZ boson pairs accompanied by a high-mass dijet system, with one W decaying leptonically and a W or Z decaying hadronically. The hadronically decaying W/Z is reconstructed as either two small-radius jets or one large-radius jet using jet substructure techniques. Constraints on the anomalous quartic gauge boson coupling parameters α4 and α5 are set by fitting the transverse mass of the diboson system, and the resulting 95% confidence intervals are -0.024<α4<0.030 and -0.028<α5<0.033..
72. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurements of top-quark pair to Z-boson cross-section ratios at √s=13 , 8, 7 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP02(2017)117, 2017, 2, 2017.02, [URL], Ratios of top-quark pair to Z-boson cross sections measured from proton-proton collisions at the LHC centre-of-mass energies of s=13 TeV, 8 TeV, and 7 TeV are presented by the ATLAS Collaboration. Single ratios, at a given s for the two processes and at different s for each process, as well as double ratios of the two processes at different s, are evaluated. The ratios are constructed using previously published ATLAS measurements of the tt¯ and Z-boson production cross sections, corrected to a common phase space where required, and a new analysis of Z → ℓ+ where ℓ = e, μ at s=13 TeV performed with data collected in 2015 with an integrated luminosity of 3.2 fb−1. Correlations of systematic uncertainties are taken into account when evaluating the uncertainties in the ratios. The correlation model is also used to evaluate the combined cross section of the Z → e+e and the Z → μ+μ channels for each s value. The results are compared to calculations performed at next-to-next-to-leading-order accuracy using recent sets of parton distribution functions. The data demonstrate significant power to constrain the gluon distribution function for the Bjorken-x values near 0.1 and the light-quark sea for x < 0.02.[Figure not available: see fulltext.].
73. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurements of charge and CP asymmetries in b-hadron decays using top-quark events collected by the ATLAS detector in pp collisions at √s=8 TeV, Journal of High Energy Physics, 10.1007/JHEP02(2017)071, 2017, 2, 2017.02, [URL], Same- and opposite-sign charge asymmetries are measured in lepton+jets tt¯ events in which a b-hadron decays semileptonically to a soft muon, using data corresponding to an integrated luminosity of 20.3 fb−1 from proton-proton collisions at a centre-of-mass energy of s=√8 TeV collected with the ATLAS detector at the Large Hadron Collider at CERN. The charge asymmetries are based on the charge of the lepton from the top-quark decay and the charge of the soft muon from the semileptonic decay of a b-hadron and are measured in a fiducial region corresponding to the experimental acceptance. Four CP asymmetries (one mixing and three direct) are measured and are found to be compatible with zero and consistent with the Standard Model.[Figure not available: see fulltext.].
74. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of the prompt J/ ψ pair production cross-section in pp collisions at √s=8 TeV with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-4644-9, 77, 2, 2017.02, [URL], The production of two prompt J/ ψ mesons, each with transverse momenta pT> 8.5 GeV and rapidity |y| < 2.1 , is studied using a sample of proton-proton collisions at s=8 TeV, corresponding to an integrated luminosity of 11.4 fb- 1 collected in 2012 with the ATLAS detector at the LHC. The differential cross-section, assuming unpolarised J/ ψ production, is measured as a function of the transverse momentum of the lower-pTJ/ ψ meson, di-J/ ψpT and mass, the difference in rapidity between the two J/ ψ mesons, and the azimuthal angle between the two J/ ψ mesons. The fraction of prompt pair events due to double parton scattering is determined by studying kinematic correlations between the two J/ ψ mesons. The total and double parton scattering cross-sections are compared with predictions. The effective cross-section of double parton scattering is measured to be σeff= 6.3 ± 1.6 (stat) ± 1.0 (syst) mb..
75. M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo,, Measurement of W boson angular distributions in events with high transverse momentum jets at √s = 8 TeV using the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2016.12.005, 765, 132-153, 2017.02, [URL], The W boson angular distribution in events with high transverse momentum jets is measured using data collected by the ATLAS experiment from proton-proton collisions at a centre-of-mass energy √s = 8 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb-1. The focus is on the contributions to W + jets processes from real W emission, which is achieved by studying events where a muon is observed close to a high transverse momentum jet. At small angular separations, these contributions are expected to be large. Various theoretical models of this process are compared to the data in terms of the absolute cross-section and the angular distributions of the muon from the leptonic W decay..
76. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for triboson W±W±W production in pp collisions at √s=8 TeV with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-4692-1, 77, 3, 2017.03, [URL], This paper reports a search for triboson W±W±W production in two decay channels (W±W±W→ ℓ±νℓ±νℓν and W±W±W→ ℓ±νℓ±νjj with ℓ= e, μ) in proton-proton collision data corresponding to an integrated luminosity of 20.3 fb - 1 at a centre-of-mass energy of 8 TeV with the ATLAS detector at the Large Hadron Collider. Events with exactly three charged leptons, or two leptons with the same electric charge in association with two jets, are selected. The total number of events observed in data is consistent with the Standard Model (SM) predictions. The observed 95% confidence level upper limit on the SM W±W±W production cross section is found to be 730 fb with an expected limit of 560 fb in the absence of SM W±W±W production. Limits are also set on WWWW anomalous quartic gauge couplings..
77. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for new phenomena in events containing a same-flavour opposite-sign dilepton pair, jets, and large missing transverse momentum in √s=13 TeV pp collisions with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-4700-5, 77, 3, 2017.03, [URL], Two searches for new phenomena in final states containing a same-flavour opposite-sign lepton (electron or muon) pair, jets, and large missing transverse momentum are presented. These searches make use of proton–proton collision data, collected during 2015 and 2016 at a centre-of-mass energy s=13 TeV by the ATLAS detector at the large hadron collider, which correspond to an integrated luminosity of 14.7fb-1. Both searches target the pair production of supersymmetric particles, squarks or gluinos, which decay to final states containing a same-flavour opposite-sign lepton pair via one of two mechanisms: a leptonically decaying Z boson in the final state, leading to a peak in the dilepton invariant-mass distribution around the Z boson mass; and decays of neutralinos (e.g. χ~20→ℓ+ℓ-χ~10), yielding a kinematic endpoint in the dilepton invariant-mass spectrum. The data are found to be consistent with the Standard Model expectation. Results are interpreted in simplified models of gluino-pair (squark-pair) production, and provide sensitivity to gluinos (squarks) with masses as large as 1.70 TeV (980 GeV)..
78. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurements of top quark spin observables in tt¯ events using dilepton final states in √s=8 TeV pp collisions with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP03(2017)113, 2017, 3, 2017.03, [URL], Measurements of top quark spin observables in tt¯ events are presented based on 20.2 fb−1 of s=8 TeV proton-proton collisions recorded with the ATLAS detector at the LHC. The analysis is performed in the dilepton final state, characterised by the presence of two isolated leptons (electrons or muons). There are 15 observables, each sensitive to a different coefficient of the spin density matrix of tt¯ production, which are measured independently. Ten of these observables are measured for the first time. All of them are corrected for detector resolution and acceptance effects back to the parton and stable-particle levels. The measured values of the observables at parton level are compared to Standard Model predictions at next-to-leading order in QCD. The corrected distributions at stable-particle level are presented and the means of the distributions are compared to Monte Carlo predictions. No significant deviation from the Standard Model is observed for any observable.[Figure not available: see fulltext.].
79. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of charged-particle distributions sensitive to the underlying event in √s=13 TeV proton-proton collisions with the ATLAS detector at the LHC, Journal of High Energy Physics, 10.1007/JHEP03(2017)157, 2017, 3, 2017.03, [URL], We present charged-particle distributions sensitive to the underlying event, measured by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV, in low-luminosity Large Hadron Collider fills corresponding to an integrated luminosity of 1.6 nb−1. The distributions were constructed using charged particles with absolute pseudorapidity less than 2.5 and with transverse momentum greater than 500 MeV, in events with at least one such charged particle with transverse momentum above 1 GeV. These distributions characterise the angular distribution of energy and particle flows with respect to the charged particle with highest transverse momentum, as a function of both that momentum and of charged-particle multiplicity. The results have been corrected for detector effects and are compared to the predictions of various Monte Carlo event generators, experimentally establishing the level of underlying-event activity at LHC Run 2 energies and providing inputs for the development of event generator modelling. The current models in use for UE modelling typically describe this data to 5% accuracy, compared with data uncertainties of less than 1%.[Figure not available: see fulltext.].
80. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Electron efficiency measurements with the ATLAS detector using 2012 LHC proton–proton collision data, European Physical Journal C, 10.1140/epjc/s10052-017-4756-2, 77, 3, 2017.03, [URL], This paper describes the algorithms for the reconstruction and identification of electrons in the central region of the ATLAS detector at the Large Hadron Collider (LHC). These algorithms were used for all ATLAS results with electrons in the final state that are based on the 2012 pp collision data produced by the LHC at s = 8 TeV. The efficiency of these algorithms, together with the charge misidentification rate, is measured in data and evaluated in simulated samples using electrons from Z→ ee, Z→ eeγ and J/ ψ→ ee decays. For these efficiency measurements, the full recorded data set, corresponding to an integrated luminosity of 20.3 fb- 1, is used. Based on a new reconstruction algorithm used in 2012, the electron reconstruction efficiency is 97% for electrons with ET= 15 GeV and 99% at ET= 50 GeV. Combining this with the efficiency of additional selection criteria to reject electrons from background processes or misidentified hadrons, the efficiency to reconstruct and identify electrons at the ATLAS experiment varies from 65 to 95%, depending on the transverse momentum of the electron and background rejection..
81. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Probing the W tb vertex structure in t-channel single-top-quark production and decay in pp collisions at √s=8 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP04(2017)124, 2017, 4, 2017.04, [URL], To probe the W tb vertex structure, top-quark and W -boson polarisation observables are measured from t-channel single-top-quark events produced in proton-proton collisions at a centre-of-mass energy of 8 TeV. The dataset corresponds to an integrated luminosity of 20.2 fb−1, recorded with the ATLAS detector at the LHC. Selected events contain one isolated electron or muon, large missing transverse momentum and exactly two jets, with one of them identified as likely to contain a b-hadron. Stringent selection requirements are applied to discriminate t-channel single-top-quark events from background. The polarisation observables are extracted from asymmetries in angular distributions measured with respect to spin quantisation axes appropriately chosen for the top quark and the W boson. The asymmetry measurements are performed at parton level by correcting the observed angular distributions for detector effects and hadronisation after subtracting the background contributions. The measured top-quark and W -boson polarisation values are in agreement with the Standard Model predictions. Limits on the imaginary part of the anomalous coupling gR are also set from model-independent measurements.[Figure not available: see fulltext.]..
82. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, M. Abolins, O. S. AbouZeid, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, G. Alimonti, L. Alio, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Performance of algorithms that reconstruct missing transverse momentum in √s = 8 TeV proton–proton collisions in the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-4780-2, 77, 4, 2017.04, [URL], The reconstruction and calibration algorithms used to calculate missing transverse momentum (ETmiss) with the ATLAS detector exploit energy deposits in the calorimeter and tracks reconstructed in the inner detector as well as the muon spectrometer. Various strategies are used to suppress effects arising from additional proton–proton interactions, called pileup, concurrent with the hard-scatter processes. Tracking information is used to distinguish contributions from the pileup interactions using their vertex separation along the beam axis. The performance of the ETmiss reconstruction algorithms, especially with respect to the amount of pileup, is evaluated using data collected in proton–proton collisions at a centre-of-mass energy of 8 TeV during 2012, and results are shown for a data sample corresponding to an integrated luminosity of 20.3fb-1. The simulation and modelling of ETmiss in events containing a Z boson decaying to two charged leptons (electrons or muons) or a W boson decaying to a charged lepton and a neutrino are compared to data. The acceptance for different event topologies, with and without high transverse momentum neutrinos, is shown for a range of threshold criteria for ETmiss , and estimates of the systematic uncertainties in the ETmiss measurements are presented..
83. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of the t t production cross section in the τ+jets final state in pp collisions at s =8 TeV using the ATLAS detector, Physical Review D, 10.1103/PhysRevD.95.072003, 95, 7, 2017.04, [URL], A measurement of the inclusive pp→tt+X production cross section in the τ+jets final state using only the hadronic decays of the τ lepton is presented. The measurement is performed using 20.2 fb-1 of proton-proton collision data recorded at a center-of-mass energy of s=8 TeV with the ATLAS detector at the Large Hadron Collider. The cross section is measured via a counting experiment by imposing a set of selection criteria on the identification and kinematic variables of the reconstructed particles and jets, and on event kinematic variables and characteristics. The production cross section is measured to be σtt=239±29 pb, which is in agreement with the measurements in other final states and the theoretical predictions at this center-of-mass energy..
84. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of the inclusive cross-sections of single top-quark and top-antiquark t-channel production in pp collisions at √s=13 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP04(2017)086, 2017, 4, 2017.04, [URL], A measurement of the t-channel single-top-quark and single-top-antiquark production cross-sections in the lepton+jets channel is presented, using 3.2 fb−1 of proton-proton collision data at a centre-of-mass energy of 13 TeV, recorded with the ATLAS detector at the LHC in 2015. Events are selected by requiring one charged lepton (electron or muon), missing transverse momentum, and two jets with high transverse momentum, exactly one of which is required to be b-tagged. Using a binned maximum-likelihood fit to the discriminant distribution of a neural network, the cross-sections are determined to be σ(tq) = 156 ± 5 (stat.) ± 27 (syst.) ± 3 (lumi.) pb for single top-quark production and σ(t¯ q) = 91 ± 4 (stat.) ± 18 (syst.) ± 2 (lumi.) pb for single top-antiquark production, assuming a top-quark mass of 172.5 GeV. The cross-section ratio is measured to be Rt=σ(tq)/σ(t¯q)=1.72±0.09 (stat.) ± 0.18 (syst.). All results are in agreement with Standard Model predictions.[Figure not available: see fulltext.].
85. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of the W boson polarisation in tt¯ events from pp collisions at √s = 8 TeV in the lepton + jets channel with ATLAS, European Physical Journal C, 10.1140/epjc/s10052-017-4819-4, 77, 4, 2017.04, [URL], This paper presents a measurement of the polarisation of W bosons from tt¯ decays, reconstructed in events with one high-pT lepton and at least four jets. Data from pp collisions at the LHC were collected at s = 8 TeV and correspond to an integrated luminosity of 20.2 fb- 1. The angle θ between the b-quark from the top quark decay and a direct W boson decay product in the W boson rest frame is sensitive to the W boson polarisation. Two different W decay products are used as polarisation analysers: the charged lepton and the down-type quark for the leptonically and hadronically decaying W boson, respectively. The most precise measurement of the W boson polarisation via the distribution of cos θ is obtained using the leptonic analyser and events in which at least two of the jets are tagged as b-quark jets. The fitted fractions of longitudinal, left- and right-handed polarisation states are F0=0.709±0.019, FL=0.299±0.015 and FR=-0.008±0.014, and are the most precisely measured W boson polarisation fractions to date. Limits on anomalous couplings of the Wtb vertex are set..
86. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of jet activity produced in top-quark events with an electron, a muon and two b-tagged jets in the final state in pp collisions at √s=13 TeV with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-4766-0, 77, 4, 2017.04, [URL], Measurements of jet activity in top-quark pair events produced in proton–proton collisions are presented, using 3.2 fb- 1of pp collision data at a centre-of-mass energy of 13 TeV collected by the ATLAS experiment at the Large Hadron Collider. Events are chosen by requiring an opposite-charge eμ pair and two b-tagged jets in the final state. The normalised differential cross-sections of top-quark pair production are presented as functions of additional-jet multiplicity and transverse momentum, pT. The fraction of signal events that do not contain additional jet activity in a given rapidity region, the gap fraction, is measured as a function of the pTthreshold for additional jets, and is also presented for different invariant mass regions of the eμbb¯ system. All measurements are corrected for detector effects and presented as particle-level distributions compared to predictions with different theoretical approaches for QCD radiation. While the kinematics of the jets from top-quark decays are described well, the generators show differing levels of agreement with the measurements of observables that depend on the production of additional jets..
87. Z. Deng, Y. Li, Y. Wang, Q. Yue, Z. Yang, D. Boumediene, C. Carloganu, V. Français, G. Cho, D. W. Kim, S. C. Lee, Z. Liu, W. Park, S. Vallecorsa, S. Cauwenbergh, M. Tytgat, A. Pingault, N. Zaganidis, O. Bach, E. Brianne, A. Ebrahimi, K. Gadow, P. Göttlicher, O. Hartbrich, A. Irles, K. Kotera, F. Krivan, K. Krüger, S. Lu, C. Neubüser, A. Provenza, M. Reinecke, F. Sefkow, S. Schuwalow, Y. Sudo, H. L. Tran, H. Hirai, Kiyotomo Kawagoe, Taikan Suehara, H. Sumida, Tamaki Yoshioka, E. Cortina Gil, S. Mannai, V. Buridon, C. Combaret, L. Caponetto, R. Eté, G. Garillot, G. Grenier, R. Han, Tracking within Hadronic Showers in the CALICE SDHCAL prototype using a Hough Transform Technique, Journal of Instrumentation, 10.1088/1748-0221/12/05/P05009, 12, 5, 2017.05, [URL], The high granularity of the CALICE Semi-Digital Hadronic CALorimeter (SDHCAL) provides the capability to reveal the track segments present in hadronic showers. These segments are then used as a tool to probe the behaviour of the active layers in situ, to better reconstruct the energy of these hadronic showers and also to distinguish them from electromagnetic ones. In addition, the comparison of these track segments in data and the simulation helps to discriminate among the different shower models used in the simulation. To extract the track segments in the showers recorded in the SDHCAL, a Hough Transform is used after being adapted to the presence of the dense core of the hadronic showers and the SDHCAL active medium structure..
88. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Reconstruction of primary vertices at the ATLAS experiment in Run 1 proton–proton collisions at the LHC, European Physical Journal C, 10.1140/epjc/s10052-017-4887-5, 77, 5, 2017.05, [URL], This paper presents the method and performance of primary vertex reconstruction in proton–proton collision data recorded by the ATLAS experiment during Run 1 of the LHC. The studies presented focus on data taken during 2012 at a centre-of-mass energy of s=8 TeV. The performance has been measured as a function of the number of interactions per bunch crossing over a wide range, from one to seventy. The measurement of the position and size of the luminous region and its use as a constraint to improve the primary vertex resolution are discussed. A longitudinal vertex position resolution of about 30μm is achieved for events with high multiplicity of reconstructed tracks. The transverse position resolution is better than 20μm and is dominated by the precision on the size of the luminous region. An analytical model is proposed to describe the primary vertex reconstruction efficiency as a function of the number of interactions per bunch crossing and of the longitudinal size of the luminous region. Agreement between the data and the predictions of this model is better than 3% up to seventy interactions per bunch crossing..
89. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Performance of the ATLAS trigger system in 2015, European Physical Journal C, 10.1140/epjc/s10052-017-4852-3, 77, 5, 2017.05, [URL], During 2015 the ATLAS experiment recorded 3.8fb-1 of proton–proton collision data at a centre-of-mass energy of 13TeV. The ATLAS trigger system is a crucial component of the experiment, responsible for selecting events of interest at a recording rate of approximately 1 kHz from up to 40 MHz of collisions. This paper presents a short overview of the changes to the trigger and data acquisition systems during the first long shutdown of the LHC and shows the performance of the trigger system and its components based on the 2015 proton–proton collision data..
90. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Performance of the ATLAS Transition Radiation Tracker in Run 1 of the LHC
Tracker properties, Journal of Instrumentation, 10.1088/1748-0221/12/05/P05002, 12, 5, 2017.05, [URL], The tracking performance parameters of the ATLAS Transition Radiation Tracker (TRT) as part of the ATLAS inner detector are described in this paper for different data-taking conditions in proton-proton, proton-lead and lead-lead collisions at the Large Hadron Collider (LHC). The performance is studied using data collected during the first period of LHC operation (Run 1) and is compared with Monte Carlo simulations. The performance of the TRT, operating with two different gas mixtures (xenon-based and argon-based) and its dependence on the TRT occupancy is presented. These studies show that the tracking performance of the TRT is similar for the two gas mixtures and that a significant contribution to the particle momentum resolution is made by the TRT up to high particle densities..
91. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurements of top-quark pair differential cross-sections in the eμ channel in pp collisions at √s=13 TeV using the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-4821-x, 77, 5, 2017.05, [URL], This article presents measurements of tt¯ differential cross-sections in a fiducial phase-space region, using an integrated luminosity of 3.2 fb- 1 of proton–proton data at a centre-of-mass energy of s=13 TeV recorded by the ATLAS experiment at the LHC in 2015. Differential cross-sections are measured as a function of the transverse momentum and absolute rapidity of the top quark, and of the transverse momentum, absolute rapidity and invariant mass of the tt¯ system. The tt¯ events are selected by requiring one electron and one muon of opposite electric charge, and at least two jets, one of which must be tagged as containing a b-hadron. The measured differential cross-sections are compared to predictions of next-to-leading order generators matched to parton showers and the measurements are found to be consistent with all models within the experimental uncertainties with the exception of the Powheg-Box+ Herwig++ predictions, which differ significantly from the data in both the transverse momentum of the top quark and the mass of the tt¯ system..
92. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, High-ET isolated-photon plus jets production in pp collisions at s=8 TeV with the ATLAS detector, Nuclear Physics B, 10.1016/j.nuclphysb.2017.03.006, 918, 257-316, 2017.05, [URL], The dynamics of isolated-photon plus one-, two- and three-jet production in pp collisions at a centre-of-mass energy of 8 TeV are studied with the ATLAS detector at the LHC using a data set with an integrated luminosity of 20.2 fb−1. Measurements of isolated-photon plus jets cross sections are presented as functions of the photon and jet transverse momenta. The cross sections as functions of the azimuthal angle between the photon and the jets, the azimuthal angle between the jets, the photon–jet invariant mass and the scattering angle in the photon–jet centre-of-mass system are presented. The pattern of QCD radiation around the photon and the leading jet is investigated by measuring jet production in an annular region centred on each object; enhancements are observed around the leading jet with respect to the photon in the directions towards the beams. The experimental measurements are compared to several different theoretical calculations, and overall a good description of the data is found..
93. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Search for dark matter at √s=13TeV in final states containing an energetic photon and large missing transverse momentum with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-4965-8, 77, 6, 2017.06, [URL], Results of a search for physics beyond the Standard Model in events containing an energetic photon and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. As the number of events observed in data, corresponding to an integrated luminosity of 36.1 fb- 1 of proton–proton collisions at a centre-of-mass energy of 13TeV, is in agreement with the Standard Model expectations, model-independent limits are set on the fiducial cross section for the production of events in this final state. Exclusion limits are also placed in models where dark-matter candidates are pair-produced. For dark-matter production via an axial-vector or a vector mediator in the s-channel, this search excludes mediator masses below 750–1200GeV for dark-matter candidate masses below 230–480GeV at 95% confidence level, depending on the couplings. In an effective theory of dark-matter production, the limits restrict the value of the suppression scale M to be above 790GeV at 95% confidence level. A limit is also reported on the production of a high-mass scalar resonance by processes beyond the Standard Model, in which the resonance decays to Zγ and the Z boson subsequently decays into neutrinos..
94. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Precision measurement and interpretation of inclusive W+ , W- and Z/ γ production cross sections with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-4911-9, 77, 6, 2017.06, [URL], High-precision measurements by the ATLAS Collaboration are presented of inclusive W+→ ℓ+ν, W-→ ℓ-ν¯ and Z/ γ→ ℓℓ (ℓ= e, μ) Drell–Yan production cross sections at the LHC. The data were collected in proton–proton collisions at s=7TeV with an integrated luminosity of 4.6fb-1. Differential W+ and W- cross sections are measured in a lepton pseudorapidity range | η| < 2.5. Differential Z/ γ cross sections are measured as a function of the absolute dilepton rapidity, for | y | < 3.6 , for three intervals of dilepton mass, m , extending from 46 to 150GeV. The integrated and differential electron- and muon-channel cross sections are combined and compared to theoretical predictions using recent sets of parton distribution functions. The data, together with the final inclusive e±p scattering cross-section data from H1 and ZEUS, are interpreted in a next-to-next-to-leading-order QCD analysis, and a new set of parton distribution functions, ATLAS-epWZ16, is obtained. The ratio of strange-to-light sea-quark densities in the proton is determined more accurately than in previous determinations based on collider data only, and is established to be close to unity in the sensitivity range of the data. A new measurement of the CKM matrix element | Vc s| is also provided..
95. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurements of the production cross section of a Z boson in association with jets in pp collisions at √s=13 TeV with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-4900-z, 77, 6, 2017.06, [URL], Measurements of the production cross section of a Z boson in association with jets in proton–proton collisions at s=13 TeV are presented, using data corresponding to an integrated luminosity of 3.16 fb- 1 collected by the ATLAS experiment at the CERN Large Hadron Collider in 2015. Inclusive and differential cross sections are measured for events containing a Z boson decaying to electrons or muons and produced in association with up to seven jets with pT> 30 GeV and.
96. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurements of integrated and differential cross sections for isolated photon pair production in pp collisions at s =8 TeV with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.95.112005, 95, 11, 2017.06, [URL], A measurement of the production cross section for two isolated photons in proton-proton collisions at a center-of-mass energy of s=8 TeV is presented. The results are based on an integrated luminosity of 20.2 fb-1 recorded by the ATLAS detector at the Large Hadron Collider. The measurement considers photons with pseudorapidities satisfying |ηγ|<1.37 or 1.56<|ηγ|<2.37 and transverse energies of respectively ET,1γ>40 GeV and ET,2γ>30 GeV for the two leading photons ordered in transverse energy produced in the interaction. The background due to hadronic jets and electrons is subtracted using data-driven techniques. The fiducial cross sections are corrected for detector effects and measured differentially as a function of six kinematic observables. The measured cross section integrated within the fiducial volume is 16.8±0.8 pb. The data are compared to fixed-order QCD calculations at next-to-leading-order and next-to-next-to-leading-order accuracy as well as next-to-leading-order computations including resummation of initial-state gluon radiation at next-to-next-to-leading logarithm or matched to a parton shower, with relative uncertainties varying from 5% to 20%..
97. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of multi-particle azimuthal correlations in pp, p + Pb and low-multiplicity Pb + Pb collisions with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-4988-1, 77, 6, 2017.06, [URL], Multi-particle cumulants and corresponding Fourier harmonics are measured for azimuthal angle distributions of charged particles in pp collisions at s = 5.02 and 13 TeV and in p + Pb collisions at sNN = 5.02 TeV, and compared to the results obtained for low-multiplicity Pb+Pb collisions at sNN = 2.76 TeV. These measurements aim to assess the collective nature of particle production. The measurements of multi-particle cumulants confirm the evidence for collective phenomena in p + Pb and low-multiplicity Pb+Pb collisions. On the other hand, the pp results for four-particle cumulants do not demonstrate collective behaviour, indicating that they may be biased by contributions from non-flow correlations. A comparison of multi-particle cumulants and derived Fourier harmonics across different collision systems is presented as a function of the charged-particle multiplicity. For a given multiplicity, the measured Fourier harmonics are largest in Pb+Pb, smaller in p + Pb and smallest in pp collisions. The pp results show no dependence on the collision energy, nor on the multiplicity..
98. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Susumu Oda, Hidetoshi Otono, Junji Tojo, Measurement of jet fragmentation in Pb+Pb and pp collisions at √sNN=2.76 TeV with the ATLAS detector at the LHC, European Physical Journal C, 10.1140/epjc/s10052-017-4915-5, 77, 6, 2017.06, [URL], The distributions of transverse momentum and longitudinal momentum fraction of charged particles in jets are measured in Pb+Pb and pp collisions with the ATLAS detector at the LHC. The distributions are measured as a function of jet transverse momentum and rapidity. The analysis utilises an integrated luminosity of 0.14 nb-1 of Pb+Pb data and 4.0 pb-1 of pp data collected in 2011 and 2013, respectively, at the same centre-of-mass energy of 2.76 TeV per colliding nucleon pair. The distributions measured in pp collisions are used as a reference for those measured in Pb+Pb collisions in order to evaluate the impact on the internal structure of jets from the jet energy loss of fast partons propagating through the hot, dense medium created in heavy-ion collisions. Modest but significant centrality-dependent modifications of fragmentation functions in Pb+Pb collisions with respect to those in pp collisions are seen. No significant dependence of modifications on jet pT and rapidity selections is observed except for the fragments with the highest transverse momenta for which some reduction of yields is observed for more forward jets..
99. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of forward-backward multiplicity correlations in lead-lead, proton-lead, and proton-proton collisions with the ATLAS detector, Physical Review C, 10.1103/PhysRevC.95.064914, 95, 6, 2017.06, [URL], Two-particle pseudorapidity correlations are measured in sNN=2.76TeVPb+Pb, sNN=5.02TeVp+Pb, and s=13TeVpp collisions at the Large Hadron Collider (LHC), with total integrated luminosities of approximately 7μb-1, 28 nb-1, and 65 nb-1, respectively. The correlation function CN(η1,η2) is measured as a function of event multiplicity using charged particles in the pseudorapidity range |η|<2.4. The correlation function contains a significant short-range component, which is estimated and subtracted. After removal of the short-range component, the shape of the correlation function is described approximately by 1+(a12)1/2η1η2 in all collision systems over the full multiplicity range. The values of (a12)1/2 are consistent for the opposite-charge pairs and same-charge pairs, and for the three collision systems at similar multiplicity. The values of (a12)1/2 and the magnitude of the short-range component both follow a power-law dependence on the event multiplicity. The short-range component in p + Pb collisions, after symmetrizing the proton and lead directions, is found to be smaller at a given η than in pp collisions with comparable multiplicity..
100. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, R. Aben, M. Abolins, O. S. AbouZeid, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, G. Alimonti, L. Alio, J. Alison, S. P. Alkire, B. M.M. Allbrooke, P. P. Allport, A. Aloisio, A. Alonso, F. Alonso, C. Alpigiani, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Topological cell clustering in the ATLAS calorimeters and its performance in LHC Run 1, European Physical Journal C, 10.1140/epjc/s10052-017-5004-5, 77, 7, 2017.07, [URL], The reconstruction of the signal from hadrons and jets emerging from the proton–proton collisions at the Large Hadron Collider (LHC) and entering the ATLAS calorimeters is based on a three-dimensional topological clustering of individual calorimeter cell signals. The cluster formation follows cell signal-significance patterns generated by electromagnetic and hadronic showers. In this, the clustering algorithm implicitly performs a topological noise suppression by removing cells with insignificant signals which are not in close proximity to cells with significant signals. The resulting topological cell clusters have shape and location information, which is exploited to apply a local energy calibration and corrections depending on the nature of the cluster. Topological cell clustering is established as a well-performing calorimeter signal definition for jet and missing transverse momentum reconstruction in ATLAS..
101. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Studies of Zγ production in association with a high-mass dijet system in pp collisions at √s=8 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP07(2017)107, 2017, 7, 2017.07, [URL], The production of a Z boson and a photon in association with a high-mass dijet system is studied using 20.2 fb−1 of proton-proton collision data at a centre-of-mass energy of s=8 TeV recorded with the ATLAS detector in 2012 at the Large Hadron Collider. Final states with a photon and a Z boson decaying into a pair of either electrons, muons, or neutrinos are analysed. Electroweak and total pp → Zγjj cross-sections are extracted in two fiducial regions with different sensitivities to electroweak production processes. Quartic couplings of vector bosons are studied in regions of phase space with an enhanced contribution from pure electroweak production, sensitive to vector-boson scattering processes VV → Zγ. No deviations from Standard Model predictions are observed and constraints are placed on anomalous couplings parameterized by higher-dimensional operators using effective field theory.[Figure not available: see fulltext.]..
102. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurements of electroweak Wjj production and constraints on anomalous gauge couplings with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-5007-2, 77, 7, 2017.07, [URL], Measurements of the electroweak production of a W boson in association with two jets at high dijet invariant mass are performed using s= 7 and 8 TeV proton–proton collision data produced by the Large Hadron Collider, corresponding respectively to 4.7 and 20.2 fb- 1 of integrated luminosity collected by the ATLAS detector. The measurements are sensitive to the production of a W boson via a triple-gauge-boson vertex and include both the fiducial and differential cross sections of the electroweak process..
103. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of the cross section for inclusive isolated-photon production in pp collisions at s=13 TeV using the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2017.04.072, 770, 473-493, 2017.07, [URL], Inclusive isolated-photon production in pp collisions at a centre-of-mass energy of 13 TeV is studied with the ATLAS detector at the LHC using a data set with an integrated luminosity of 3.2 fb−1. The cross section is measured as a function of the photon transverse energy above 125 GeV in different regions of photon pseudorapidity. Next-to-leading-order perturbative QCD and Monte Carlo event-generator predictions are compared to the cross-section measurements and provide an adequate description of the data..
104. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Jet reconstruction and performance using particle flow with the ATLAS Detector, European Physical Journal C, 10.1140/epjc/s10052-017-5031-2, 77, 7, 2017.07, [URL], This paper describes the implementation and performance of a particle flow algorithm applied to 20.2 fb- 1 of ATLAS data from 8 TeV proton–proton collisions in Run 1 of the LHC. The algorithm removes calorimeter energy deposits due to charged hadrons from consideration during jet reconstruction, instead using measurements of their momenta from the inner tracker. This improves the accuracy of the charged-hadron measurement, while retaining the calorimeter measurements of neutral-particle energies. The paper places emphasis on how this is achieved, while minimising double-counting of charged-hadron signals between the inner tracker and calorimeter. The performance of particle flow jets, formed from the ensemble of signals from the calorimeter and the inner tracker, is compared to that of jets reconstructed from calorimeter energy deposits alone, demonstrating improvements in resolution and pile-up stability..
105. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for the Dimuon Decay of the Higgs Boson in pp Collisions at s =13 TeV with the ATLAS Detector, Physical Review Letters, 10.1103/PhysRevLett.119.051802, 119, 5, 2017.08, [URL], A search for the dimuon decay of the Higgs boson was performed using data corresponding to an integrated luminosity of 36.1 fb-1 collected with the ATLAS detector in pp collisions at s=13 TeV at the Large Hadron Collider. No significant excess is observed above the expected background. The observed (expected) upper limit on the cross section times branching ratio is 3.0 (3.1) times the Standard Model prediction at the 95% confidence level for a Higgs boson mass of 125 GeV. When combined with the pp collision data at s=7 TeV and s=8 TeV, the observed (expected) upper limit is 2.8 (2.9) times the Standard Model prediction..
106. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J.Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for pair production of vector-like top quarks in events with one lepton, jets, and missing transverse momentum in √s=13 TeV pp collisions with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP08(2017)052, 2017, 8, 2017.08, [URL], The results of a search for vector-like top quarks using events with exactly one lepton, at least four jets, and large missing transverse momentum are reported. The search is optimised for pair production of vector-like top quarks in the Z() t + X decay channel. LHC pp collision data at a centre-of-mass energy of s=13 TeV recorded by the ATLAS detector in 2015 and 2016 are used, corresponding to an integrated luminosity of 36.1 fb−1. No significant excess over the Standard Model expectation is seen and upper limits on the production cross-section of a vector-like T quark pair as a function of the T quark mass are derived. The observed (expected) 95% CL lower limits on the T mass are 870 GeV (890 GeV) for the weak-isospin singlet model, 1.05 TeV (1.06 TeV) for the weak-isospin doublet model and 1.16 TeV (1.17 TeV) for the pure Zt decay mode. Limits are also set on the mass as a function of the decay branching ratios, excluding large parts of the parameter space for masses below 1 TeV.[Figure not available: see fulltext.]..
107. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for direct top squark pair production in events with a Higgs or Z boson, and missing transverse momentum in √s=13 TeV pp collisions with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP08(2017)006, 2017, 8, 2017.08, [URL], A search for direct top squark pair production resulting in events with either a same-flavour opposite-sign dilepton pair with invariant mass compatible with a Z boson or a pair of jets compatible with a Standard Model (SM) Higgs boson (h) is presented. Requirements on the missing transverse momentum, together with additional selections on leptons, jets, jets identified as originating from b-quarks are imposed to target the other decay products of the top squark pair. The analysis is performed using proton-proton collision data at s=13 TeV collected with the ATLAS detector at the LHC in 2015–2016, corresponding to an integrated luminosity of 36.1 fb−1. No excess is observed in the data with respect to the SM predictions. The results are interpreted in two sets of models. In the first set, direct production of pairs of lighter top squarks (t˜ 1) with long decay chains involving Z or Higgs bosons is considered. The second set includes direct pair production of the heavier top squark pairs (t˜ 2) decaying via t˜ 2→ Zt˜ 1 or t˜ 2→ ht˜ 1. The results exclude at 95% confidence level t˜ 2 and t˜ 1 masses up to about 800 GeV, extending the exclusion region of supersymmetric parameter space covered by previous LHC searches.[Figure not available: see fulltext.]..
108. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurements of long-range azimuthal anisotropies and associated Fourier coefficients for pp collisions at s =5.02 and 13 TeV and p+Pb collisions at sNN =5.02 TeV with the ATLAS detector, Physical Review C, 10.1103/PhysRevC.96.024908, 96, 2, 2017.08, [URL], ATLAS measurements of two-particle correlations are presented for s=5.02 and 13 TeV pp collisions and for sNN=5.02 TeV p+Pb collisions at the LHC. The correlation functions are measured as a function of relative azimuthal angle Δφ, and pseudorapidity separation Δη, using charged particles detected within the pseudorapidity interval |η|<2.5. Azimuthal modulation in the long-range component of the correlation function, with |Δη|>2, is studied using a template fitting procedure to remove a "back-to-back" contribution to the correlation function that primarily arises from hard-scattering processes. In addition to the elliptic, cos(2Δφ), modulation observed in a previous measurement, the pp correlation functions exhibit significant cos(3Δφ) and cos(4Δφ) modulation. The Fourier coefficients vn,n associated with the cos(nΔφ) modulation of the correlation functions for n=2-4 are measured as a function of charged-particle multiplicity and charged-particle transverse momentum. The Fourier coefficients are observed to be compatible with cos(nφ) modulation of per-event single-particle azimuthal angle distributions. The single-particle Fourier coefficients vn are measured as a function of charged-particle multiplicity, and charged-particle transverse momentum for n=2-4. The integrated luminosities used in this analysis are, 64 nb-1 for the s=13 TeV pp data, 170 nb-1 for the s=5.02 TeV pp data, and 28 nb-1 for the sNN=5.02 TeV p+Pb data..
109. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of the k t splitting scales in Z → ℓℓ events in pp collisions at √s=8 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP08(2017)026, 2017, 8, 2017.08, [URL], A measurement of the splitting scales occuring in the kt jet-clustering algorithm is presented for final states containing a Z boson. The measurement is done using 20.2 fb−1 of proton-proton collision data collected at a centre-of-mass energy of s=8 TeV by the ATLAS experiment at the LHC in 2012. The measurement is based on chargedparticle track information, which is measured with excellent precision in the pT region relevant for the transition between the perturbative and the non-perturbative regimes. The data distributions are corrected for detector effects, and are found to deviate from state-of-the-art predictions in various regions of the observables.[Figure not available: see fulltext.]..
110. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of WW/ WZ? l?qq' production with the hadronically decaying boson reconstructed as one or two jets in pp collisions at vs=8TeV with ATLAS, and constraints on anomalous gauge couplings, European Physical Journal C, 10.1140/epjc/s10052-017-5084-2, 77, 8, 2017.08, [URL], This paper presents a study of the production of WW or WZ boson pairs, with one W boson decaying to e? or µ? and one W or Z boson decaying hadronically. The analysis uses 20.2fb-1 of s=8TeVpp collision data, collected by the ATLAS detector at the Large Hadron Collider. Cross-sections for WW / WZ production are measured in high-pT fiducial regions defined close to the experimental event selection. The cross-section is measured for the case where the hadronically decaying boson is reconstructed as two resolved jets, and the case where it is reconstructed as a single jet. The transverse momentum distribution of the hadronically decaying boson is used to search for new physics. Observations are consistent with the Standard Model predictions, and 95% confidence intervals are calculated for parameters describing anomalous triple gauge-boson couplings..
111. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Fiducial, total and differential cross-section measurements of t-channel single top-quark production in pp collisions at 8 TeV using data collected by the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-5061-9, 77, 8, 2017.08, [URL], Detailed measurements of t-channel single top-quark production are presented. They use 20.2 fb- 1 of data collected by the ATLAS experiment in proton–proton collisions at a centre-of-mass energy of 8 TeV at the LHC. Total, fiducial and differential cross-sections are measured for both top-quark and top-antiquark production. The fiducial cross-section is measured with a precision of 5.8% (top quark) and 7.8% (top antiquark), respectively. The total cross-sections are measured to be σtot(tq)=56.7-3.8+4.3pb for top-quark production and σtot(t¯q)=32.9-2.7+3.0pb for top-antiquark production, in agreement with the Standard Model prediction. In addition, the ratio of top-quark to top-antiquark production cross-sections is determined to be Rt= 1.72 ± 0.09. The differential cross-sections as a function of the transverse momentum and rapidity of both the top quark and the top antiquark are measured at both the parton and particle levels. The transverse momentum and rapidity differential cross-sections of the accompanying jet from the t-channel scattering are measured at particle level. All measurements are compared to various Monte Carlo predictions as well as to fixed-order QCD calculations where available..
112. , G. Aad, B. Abbott, J. Abdallah, O. Abdinov, R. Aben, M. Abolins, O. S. AbouZeid, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, G. Alimonti, L. Alio, J. Alison, S. P. Alkire, B. M.M. Allbrooke, P. P. Allport, A. Aloisio, A. Alonso, F. Alonso, C. Alpigiani, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Erratum to
Measurement of the charge asymmetry in top-quark pair production in the lepton-plus-jets final state in pp collision data at √s = 8 TeV with the ATLAS detector (The European Physical Journal C, (2016), 76, 2, (87), 10.1140/epjc/s10052-016-3910-6), European Physical Journal C, 10.1140/epjc/s10052-017-5089-x, 77, 8, 2017.08, [URL], In the original paper, Fig. 4 contains the wrong label preliminary. The label has been fixed, while none of the results have changed.(Table Presented.)..
113. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Top-quark mass measurement in the all-hadronic tt¯ decay channel at √s=8 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP09(2017)118, 2017, 9, 2017.09, [URL], The top-quark mass is measured in the all-hadronic top-antitop quark decay channel using proton-proton collisions at a centre-of-mass energy of s=8 TeV with the ATLAS detector at the CERN Large Hadron Collider. The data set used in the analysis corresponds to an integrated luminosity of 20.2 fb−1. The large multi-jet background is modelled using a data-driven method. The top-quark mass is obtained from template fits to the ratio of the three-jet to the dijet mass. The three-jet mass is obtained from the three jets assigned to the top quark decay. From these three jets the dijet mass is obtained using the two jets assigned to the W boson decay. The top-quark mass is measured to be 173.72 ± 0.55 (stat.) ± 1.01 (syst.) GeV.[Figure not available: see fulltext.]..
114. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Study of WWγ and WZγ production in pp collisions at √s=8TeV and search for anomalous quartic gauge couplings with the ATLAS experiment, European Physical Journal C, 10.1140/epjc/s10052-017-5180-3, 77, 9, 2017.09, [URL], This paper presents a study of WWγ and WZγ triboson production using events from proton–proton collisions at a centre-of-mass energy of s=8TeV recorded with the ATLAS detector at the LHC and corresponding to an integrated luminosity of 20.2 fb- 1. The WWγ production cross-section is determined using a final state containing an electron, a muon, a photon, and neutrinos (e). Upper limits on the production cross-section of the e final state and the WWγ and WZγ final states containing an electron or a muon, two jets, a photon, and a neutrino (eνjjγ or μνjjγ) are also derived. The results are compared to the cross-sections predicted by the Standard Model at next-to-leading order in the strong-coupling constant. In addition, upper limits on the production cross-sections are derived in a fiducial region optimised for a search for new physics beyond the Standard Model. The results are interpreted in the context of anomalous quartic gauge couplings using an effective field theory. Confidence intervals at 95% confidence level are derived for the 14 coupling coefficients to which WWγ and WZγ production are sensitive..
115. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for supersymmetry in final states with two same-sign or three leptons and jets using 36 fb−1 of √s=13 TeV pp collision data with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP09(2017)084, 2017, 9, 2017.09, [URL], A search for strongly produced supersymmetric particles using signatures involving multiple energetic jets and either two isolated same-sign leptons (e or μ), or at least three isolated leptons, is presented. The analysis relies on the identification of b-jets and high missing transverse momentum to achieve good sensitivity. A data sample of proton-proton collisions at s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to a total integrated luminosity of 36.1 fb−1, is used for the search. No significant excess over the Standard Model prediction is observed. The results are interpreted in several simplified supersymmetric models featuring R-parity conservation or R-parity violation, extending the exclusion limits from previous searches. In models considering gluino pair production, gluino masses are excluded up to 1.87 TeV at 95% confidence level. When bottom squarks are pair-produced and decay to a chargino and a top quark, models with bottom squark masses below 700 GeV and light neutralinos are excluded at 95% confidence level. In addition, model-independent limits are set on a possible contribution of new phenomena to the signal region yields.[Figure not available: see fulltext.]..
116. M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for new phenomena in dijet events using 37 fb-1 of pp collision data collected at s =13 TeV with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.96.052004, 96, 5, 2017.09, [URL], Dijet events are studied in the proton-proton collision data set recorded at s=13 TeV with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to integrated luminosities of 3.5 fb-1 and 33.5 fb-1 respectively. Invariant mass and angular distributions are compared to background predictions and no significant deviation is observed. For resonance searches, a new method for fitting the background component of the invariant mass distribution is employed. The data set is then used to set upper limits at a 95% confidence level on a range of new physics scenarios. Excited quarks with masses below 6.0 TeV are excluded, and limits are set on quantum black holes, heavy W′ bosons, W∗ bosons, and a range of masses and couplings in a Z′ dark matter mediator model. Model-independent limits on signals with a Gaussian shape are also set, using a new approach allowing factorization of physics and detector effects. From the angular distributions, a scale of new physics in contact interaction models is excluded for scenarios with either constructive or destructive interference. These results represent a substantial improvement over those obtained previously with lower integrated luminosity..
117. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for new phenomena in a lepton plus high jet multiplicity final state with the ATLAS experiment using √s=13 TeV proton-proton collision data, Journal of High Energy Physics, 10.1007/JHEP09(2017)088, 2017, 9, 2017.09, [URL], A search for new phenomena in final states characterized by high jet multiplicity, an isolated lepton (electron or muon) and either zero or at least three b-tagged jets is presented. The search uses 36.1 fb−1 of s=13 TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider in 2015 and 2016. The dominant sources of background are estimated using parameterized extrapolations, based on observables at medium jet multiplicity, to predict the b-tagged jet multiplicity distribution at the higher jet multiplicities used in the search. No significant excess over the Standard Model expectation is observed and 95% confidence-level limits are extracted constraining four simplified models of R-parity-violating supersymmetry that feature either gluino or top-squark pair production. The exclusion limits reach as high as 2.1 TeV in gluino mass and 1.2 TeV in top-squark mass in the models considered. In addition, an upper limit is set on the cross-section for Standard Model tt¯ tt¯ production of 60 fb (6.5 × the Standard Model prediction) at 95% confidence level. Finally, model-independent limits are set on the contribution from new phenomena to the signal-region yields.[Figure not available: see fulltext.]..
118. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of the inclusive jet cross-sections in proton-proton collisions at √s=8 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP09(2017)020, 2017, 9, 2017.09, [URL], Inclusive jet production cross-sections are measured in proton-proton collisions at a centre-of-mass energy of s=8 TeV recorded by the ATLAS experiment at the Large Hadron Collider at CERN. The total integrated luminosity of the analysed data set amounts to 20.2 fb−1. Double-differential cross-sections are measured for jets defined by the anti-kt jet clustering algorithm with radius parameters of R = 0.4 and R = 0.6 and are presented as a function of the jet transverse momentum, in the range between 70 GeV and 2.5 TeV and in six bins of the absolute jet rapidity, between 0 and 3.0. The measured cross-sections are compared to predictions of quantum chromodynamics, calculated at next-to-leading order in perturbation theory, and corrected for non-perturbative and electroweak effects. The level of agreement with predictions, using a selection of different parton distribution functions for the proton, is quantified. Tensions between the data and the theory predictions are observed.[Figure not available: see fulltext.].
119. M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Identification and rejection of pile-up jets at high pseudorapidity with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-5081-5, 77, 9, 2017.09, [URL], The rejection of forward jets originating from additional proton–proton interactions (pile-up) is crucial for a variety of physics analyses at the LHC, including Standard Model measurements and searches for physics beyond the Standard Model. The identification of such jets is challenging due to the lack of track and vertex information in the pseudorapidity range | η| > 2.5. This paper presents a novel strategy for forward pile-up jet tagging that exploits jet shapes and topological jet correlations in pile-up interactions. Measurements of the per-jet tagging efficiency are presented using a data set of 3.2 fb- 1 of proton–proton collisions at a centre-of-mass energy of 13 TeV collected with the ATLAS detector. The fraction of pile-up jets rejected in the range 2.5 < | η| < 4.5 is estimated in simulated events with an average of 22 interactions per bunch-crossing. It increases with jet transverse momentum and, for jets with transverse momentum between 20 and 50 GeV, it ranges between 49% and 67% with an efficiency of 85% for selecting hard-scatter jets. A case study is performed in Higgs boson production via the vector-boson fusion process, showing that these techniques mitigate the background growth due to additional proton–proton interactions, thus enhancing the reach for such signatures..
120. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC, Nature Physics, 10.1038/nphys4208, 13, 9, 852-858, 2017.09, [URL], Light-by-light scattering (γγ → γγ) is a quantum-mechanical process that is forbidden in the classical theory of electrodynamics. This reaction is accessible at the Large Hadron Collider thanks to the large electromagnetic field strengths generated by ultra-relativistic colliding lead ions. Using 480 μ1 of lead-lead collision data recorded at a centre-of-mass energy per nucleon pair of 5.02 TeV by the ATLAS detector, here we report evidence for light-by-light scattering. A total of 13 candidate events were observed with an expected background of 2.6 ± 0.7 events. After background subtraction and analysis corrections, the fiducial cross-section of the process Pb + Pb (γγ) → Pb(∗) + Pb(∗) γγ,for photon transverse energy ET > 3GeV, photon absolute pseudorapidity |η| <2.4, diphoton invariant mass greater than 6GeV, diphoton transverse momentum lower than 2GeV and diphoton acoplanarity below 0.01, is measured to be 70 ± 24 (stat.) ±17 (syst.) nb, which is in agreement with the standard model predictions..
121. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Searches for the Zγ decay mode of the Higgs boson and for new high-mass resonances in pp collisions at √s=13 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP10(2017)112, 2017, 10, 2017.10, [URL], This article presents searches for the Zγ decay of the Higgs boson and for narrow high-mass resonances decaying to Zγ, exploiting Z boson decays to pairs of electrons or muons. The data analysis uses 36.1 fb−1 of pp collisions at s=13 recorded by the ATLAS detector at the CERN Large Hadron Collider. The data are found to be consistent with the expected Standard Model background. The observed (expected — assuming Standard Model pp → H → Zγ production and decay) upper limit on the production cross section times the branching ratio for pp → H → Zγ is 6.6. (5.2) times the Standard Model prediction at the 95% confidence level for a Higgs boson mass of 125.09 GeV. In addition, upper limits are set on the production cross section times the branching ratio as a function of the mass of a narrow resonance between 250 GeV and 2.4 TeV, assuming spin-0 resonances produced via gluon-gluon fusion, and spin-2 resonances produced via gluon-gluon or quark-antiquark initial states. For high-mass spin-0 resonances, the observed (expected) limits vary between 88 fb (61 fb) and 2.8 fb (2.7 fb) for the mass range from 250 GeV to 2.4 TeV at the 95% confidence level..
122. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for top quark decays t → qH, with H → γγ, in √s=13 TeV pp collisions using the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP10(2017)129, 2017, 10, 2017.10, [URL], This article presents a search for flavour-changing neutral currents in the decay of a top quark into an up-type (q = c, u) quark and a Higgs boson, where the Higgs boson decays into two photons. The proton-proton collision data set analysed amounts to 36.1 fb−1 at s=13 TeV collected by the ATLAS experiment at the LHC. Top quark pair events are searched for, where one top quark decays into qH and the other decays into bW. Both the hadronic and leptonic decay modes of the W boson are used. No significant excess is observed and an upper limit is set on the t → cH branching ratio of 2.2 × 10−3 at the 95% confidence level, while the expected limit in the absence of signal is 1.6 × 10−3. The corresponding limit on the tcH coupling is 0.090 at the 95% confidence level. The observed upper limit on the t → uH branching ratio is 2.4 × 10−3.[Figure not available: see fulltext.]..
123. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for pair production of heavy vector-like quarks decaying to high-p T W bosons and b quarks in the lepton-plus-jets final state in pp collisions at √s=13 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP10(2017)141, 2017, 10, 2017.10, [URL], A search is presented for the pair production of heavy vector-like T quarks, primarily targeting the T quark decays to a W boson and a b-quark. The search is based on 36.1 fb−1 of pp collisions at s=13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Data are analysed in the lepton-plus-jets final state, including at least one b-tagged jet and a large-radius jet identified as originating from the hadronic decay of a high-momentum W boson. No significant deviation from the Standard Model expectation is observed in the reconstructed T mass distribution. The observed 95% confidence level lower limit on the T mass are 1350 GeV assuming 100% branching ratio to Wb. In the SU(2) singlet scenario, the lower mass limit is 1170 GeV. This search is also sensitive to a heavy vector-like B quark decaying to Wt and other final states. The results are thus reinterpreted to provide a 95% confidence level lower limit on the B quark mass at 1250 GeV assuming 100% branching ratio to Wt; in the SU(2) singlet scenario, the limit is 1080 GeV. Mass limits on both T and B production are also set as a function of the decay branching ratios. The 100% branching ratio limits are found to be applicable to heavy vector-like Y and X production that decay to Wb and Wt, respectively..
124. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for new high-mass phenomena in the dilepton final state using 36 fb−1 of proton-proton collision data at √s=13 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP10(2017)182, 2017, 10, 2017.10, [URL], A search is conducted for new resonant and non-resonant high-mass phenomena in dielectron and dimuon final states. The search uses 36.1 fb−1 of proton-proton collision data, collected at s=13 TeV by the ATLAS experiment at the LHC in 2015 and 2016. No significant deviation from the Standard Model prediction is observed. Upper limits at 95% credibility level are set on the cross-section times branching ratio for resonances decaying into dileptons, which are converted to lower limits on the resonance mass, up to 4.1 TeV for the E6-motivated Zχ . Lower limits on the qqℓℓ contact interaction scale are set between 2.4 TeV and 40 TeV, depending on the model..
125. M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Performance of the ATLAS track reconstruction algorithms in dense environments in LHC Run 2, European Physical Journal C, 10.1140/epjc/s10052-017-5225-7, 77, 10, 2017.10, [URL], With the increase in energy of the Large Hadron Collider to a centre-of-mass energy of 13 TeV for Run 2, events with dense environments, such as in the cores of high-energy jets, became a focus for new physics searches as well as measurements of the Standard Model. These environments are characterized by charged-particle separations of the order of the tracking detectors sensor granularity. Basic track quantities are compared between 3.2 fb- 1 of data collected by the ATLAS experiment and simulation of proton–proton collisions producing high-transverse-momentum jets at a centre-of-mass energy of 13 TeV. The impact of charged-particle separations and multiplicities on the track reconstruction performance is discussed. The track reconstruction efficiency in the cores of jets with transverse momenta between 200 and 1600 GeV is quantified using a novel, data-driven, method. The method uses the energy loss, dE/dx, to identify pixel clusters originating from two charged particles. Of the charged particles creating these clusters, the measured fraction that fail to be reconstructed is 0.061±0.006(stat.)±0.014(syst.) and 0.093±0.017(stat.)±0.021(syst.) for jet transverse momenta of 200–400 GeV and 1400–1600 GeV , respectively..
126. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of the W+W production cross section in pp collisions at a centre-of-mass energy of s=13 TeV with the ATLAS experiment, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2017.08.047, 773, 354-374, 2017.10, [URL], The production of opposite-charge W-boson pairs in proton–proton collisions at s=13 TeV is measured using data corresponding to 3.16 fb−1 of integrated luminosity collected by the ATLAS detector at the CERN Large Hadron Collider in 2015. Candidate W-boson pairs are selected by identifying their leptonic decays into an electron, a muon and neutrinos. Events with reconstructed jets are not included in the candidate event sample. The cross-section measurement is performed in a fiducial phase space close to the experimental acceptance and is compared to theoretical predictions. Agreement is found between the measurement and the most accurate calculations available..
127. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of inclusive and differential cross sections in the H → ZZ * → 4ℓ decay channel in pp collisions at √s=13 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP10(2017)132, 2017, 10, 2017.10, [URL], Inclusive and differential fiducial cross sections of Higgs boson production in proton-proton collisions are measured in the H → ZZ* → 4ℓ decay channel. The proton-proton collision data were produced at the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector in 2015 and 2016, corresponding to an integrated luminosity of 36.1 fb−1. The inclusive fiducial cross section in the H → ZZ* → 4ℓ decay channel is measured to be 3.62 ± 0.50(stat)− 0.20 + 0.25 (sys) fb, in agreement with the Standard Model prediction of 2.91 ± 0.13 fb. The cross section is also extrapolated to the total phase space including all Standard Model Higgs boson decays. Several differential fiducial cross sections are measured for observables sensitive to the Higgs boson production and decay, including kinematic distributions of jets produced in association with the Higgs boson. Good agreement is found between data and Standard Model predictions. The results are used to put constraints on anomalous Higgs boson interactions with Standard Model particles, using the pseudo-observable extension to the kappa-framework.[Figure not available: see fulltext.]..
128. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Jet energy scale measurements and their systematic uncertainties in proton-proton collisions at s =13 TeV with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.96.072002, 96, 7, 2017.10, [URL], Jet energy scale measurements and their systematic uncertainties are reported for jets measured with the ATLAS detector using proton-proton collision data with a center-of-mass energy of s=13 TeV, corresponding to an integrated luminosity of 3.2 fb-1 collected during 2015 at the LHC. Jets are reconstructed from energy deposits forming topological clusters of calorimeter cells, using the anti-kt algorithm with radius parameter R=0.4. Jets are calibrated with a series of simulation-based corrections and in situ techniques. In situ techniques exploit the transverse momentum balance between a jet and a reference object such as a photon, Z boson, or multijet system for jets with 200.8) is derived from dijet pT balance measurements. For jets of pT=80 GeV, the additional uncertainty for the forward jet calibration reaches its largest value of about 2% in the range |η|>3.5 and in a narrow slice of 2.2<|η|<2.4..
129. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Correction to
Identification and rejection of pile-up jets at high pseudorapidity with the ATLAS detector (Eur. Phys. J. C, (2017), 77, (580), 10.1140/epjc/s10052-017-5081-5), European Physical Journal C, 10.1140/epjc/s10052-017-5245-3, 77, 10, 2017.10, [URL], Unfortunately, in the original version of this article the copyright holder was wrong in the HTML. The original article has been corrected..
130. M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Study of ordered hadron chains with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.96.092008, 96, 9, 2017.11, [URL], The analysis of the momentum difference between charged hadrons in high-energy proton-proton collisions is performed in order to study coherent particle production. The observed correlation pattern agrees with a model of a helical QCD string fragmenting into a chain of ground-state hadrons. A threshold momentum difference in the production of adjacent pairs of charged hadrons is observed, in agreement with model predictions. The presence of low-mass hadron chains also explains the emergence of charge-combination-dependent two-particle correlations commonly attributed to Bose-Einstein interference. The data sample consists of 190 μb-1 of minimum-bias events collected with proton-proton collisions at a center-of-mass energy s=7 TeV in the early low-luminosity data taking with the ATLAS detector at the LHC..
131. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for supersymmetry in events with b-tagged jets and missing transverse momentum in pp collisions at √s=13 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP11(2017)195, 2017, 11, 2017.11, [URL], A search for the supersymmetric partners of the Standard Model bottom and top quarks is presented. The search uses 36.1 fb−1 of pp collision data at s=13 TeV collected by the ATLAS experiment at the Large Hadron Collider. Direct production of pairs of bottom and top squarks (b¯ 1 and t¯ 1) is searched for in final states with b-tagged jets and missing transverse momentum. Distinctive selections are defined with either no charged leptons (electrons or muons) in the final state, or one charged lepton. The zero-lepton selection targets models in which the b¯ 1 is the lightest squark and decays via b¯1→bχ¯10, where χ¯10 is the lightest neutralino. The one-lepton final state targets models where bottom or top squarks are produced and can decay into multiple channels, b¯1→bχ¯10 and b¯1→t or t¯1→tχ¯10 and t¯1→b where χ¯1± is the lightest chargino and the mass difference mχ¯1±−mχ¯10 is set to 1 GeV. No excess above the expected Standard Model background is observed. Exclusion limits at 95% confidence level on the mass of third-generation squarks are derived in various supersymmetry-inspired simplified models..
132. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for heavy resonances decaying to a W or Z boson and a Higgs boson in the qq¯(′)bb¯ final state in pp collisions at s=13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2017.09.066, 774, 494-515, 2017.11, [URL], A search for heavy resonances decaying to a W or Z boson and a Higgs boson in the qq¯(′)bb¯ final state is described. The search uses 36.1 fb−1 of proton–proton collision data at s=13 TeV collected by the ATLAS detector at the CERN Large Hadron Collider in 2015 and 2016. The data are in agreement with the Standard Model expectations, with the largest excess found at a resonance mass of 3.0 TeV with a local (global) significance of 3.3 (2.1) σ. The results are presented in terms of constraints on a simplified model with a heavy vector triplet. Upper limits are set on the production cross-section times branching ratio for resonances decaying to a W (Z) boson and a Higgs boson, itself decaying to bb¯, in the mass range between 1.1 and 3.8 TeV at 95% confidence level; the limits range between 83 and 1.6 fb (77 and 1.1 fb) at 95% confidence level..
133. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for Heavy Higgs Bosons A /H Decaying to a Top Quark Pair in pp Collisions at s =8 TeV with the ATLAS Detector, Physical Review Letters, 10.1103/PhysRevLett.119.191803, 119, 19, 2017.11, [URL], A search for heavy pseudoscalar (A) and scalar (H) Higgs bosons decaying into a top quark pair (tt) has been performed with 20.3 fb-1 of proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider at a center-of-mass energy s=8 TeV. Interference effects between the signal process and standard model tt production, which are expected to distort the signal shape from a single peak to a peak-dip structure, are taken into account. No significant deviation from the standard model prediction is observed in the tt invariant mass spectrum in final states with an electron or muon, large missing transverse momentum, and at least four jets. The results are interpreted within the context of a type-II two-Higgs-doublet model. Exclusion limits on the signal strength are derived as a function of the mass mA/H and the ratio of the vacuum expectation values of the two Higgs fields, tanβ, for mA/H>500 GeV..
134. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for Dark Matter Produced in Association with a Higgs Boson Decaying to b b Using 36 fb-1 of pp Collisions at s =13 TeV with the ATLAS Detector, Physical Review Letters, 10.1103/PhysRevLett.119.181804, 119, 18, 2017.11, [URL], Several extensions of the standard model predict associated production of dark-matter particles with a Higgs boson. Such processes are searched for in final states with missing transverse momentum and a Higgs boson decaying to a bb pair with the ATLAS detector using 36.1 fb-1 of pp collisions at a center-of-mass energy of 13 TeV at the LHC. The observed data are in agreement with the standard model predictions and limits are placed on the associated production of dark-matter particles and a Higgs boson..
135. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurements of top-quark pair differential cross-sections in the lepton+jets channel in pp collisions at √s=13 TeV using the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP11(2017)191, 2017, 11, 2017.11, [URL], Measurements of differential cross-sections of top-quark pair production in fiducial phase-spaces are presented as a function of top-quark and tt¯ system kinematic observables in proton-proton collisions at a centre-of-mass energy of s=13 TeV. The data set corresponds to an integrated luminosity of 3.2 fb−1, recorded in 2015 with the ATLAS detector at the CERN Large Hadron Collider. Events with exactly one electron or muon and at least two jets in the final state are used for the measurement. Two separate selections are applied that each focus on different top-quark momentum regions, referred to as resolved and boosted topologies of the tt¯ final state. The measured spectra are corrected for detector effects and are compared to several Monte Carlo simulations by means of calculated χ2 and p-values..
136. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of the tt¯ γ production cross section in proton-proton collisions at √s=8 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP11(2017)086, 2017, 11, 2017.11, [URL], The cross section of a top-quark pair produced in association with a photon is measured in proton-proton collisions at a centre-of-mass energy of s=8 TeV with 20.2 fb−1 of data collected by the ATLAS detector at the Large Hadron Collider in 2012. The measurement is performed by selecting events that contain a photon with transverse momentum pT > 15 GeV, an isolated lepton with large transverse momentum, large missing transverse momentum, and at least four jets, where at least one is identified as originating from a b-quark. The production cross section is measured in a fiducial region close to the selection requirements. It is found to be 139 ± 7 (stat.) ± 17 (syst.) fb, in good agreement with the theoretical prediction at next-to-leading order of 151 ± 24 fb. In addition, differential cross sections in the fiducial region are measured as a function of the transverse momentum and pseudorapidity of the photon.[Figure not available: see fulltext.]..
137. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of lepton differential distributions and the top quark mass in tt¯ production in pp collisions at √s=8 TeV with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-5349-9, 77, 11, 2017.11, [URL], This paper presents single lepton and dilepton kinematic distributions measured in dileptonic tt¯ events produced in 20.2fb - 1 of s=8 TeV pp collisions recorded by the ATLAS experiment at the LHC. Both absolute and normalised differential cross-sections are measured, using events with an opposite-charge eμ pair and one or two b-tagged jets. The cross-sections are measured in a fiducial region corresponding to the detector acceptance for leptons, and are compared to the predictions from a variety of Monte Carlo event generators, as well as fixed-order QCD calculations, exploring the sensitivity of the cross-sections to the gluon parton distribution function. Some of the distributions are also sensitive to the top quark pole mass; a combined fit of NLO fixed-order predictions to all the measured distributions yields a top quark mass value of mtpole=173.2±0.9±0.8±1.2 GeV, where the three uncertainties arise from data statistics, experimental systematics, and theoretical sources..
138. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of jet pT correlations in Pb + Pb and pp collisions at sNN=2.76 TeVwith the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2017.09.078, 774, 379-402, 2017.11, [URL], Measurements of dijet pT correlations in Pb+Pb and pp collisions at a nucleon–nucleon centre-of-mass energy of sNN=2.76 TeV are presented. The measurements are performed with the ATLAS detector at the Large Hadron Collider using Pb+Pb and pp data samples corresponding to integrated luminosities of 0.14 nb−1 and 4.0 pb−1, respectively. Jets are reconstructed using the anti-kt algorithm with radius parameter values R=0.3 and R=0.4. A background subtraction procedure is applied to correct the jets for the large underlying event present in Pb+Pb collisions. The leading and sub-leading jet transverse momenta are denoted pT1 and pT2 . An unfolding procedure is applied to the two-dimensional (pT1 ,pT2 ) distributions to account for experimental effects in the measurement of both jets. Distributions of (1/N)dN/dxJ, where xJ=pT2 /pT1 , are presented as a function of pT1 and collision centrality. The distributions are found to be similar in peripheral Pb+Pb collisions and pp collisions, but highly modified in central Pb+Pb collisions. Similar features are present in both the R=0.3 and R=0.4 results, indicating that the effects of the underlying event are properly accounted for in the measurement. The results are qualitatively consistent with expectations from partonic energy loss models..
139. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of detector-corrected observables sensitive to the anomalous production of events with jets and large missing transverse momentum in pp collisions at √s=13 TeV using the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-5315-6, 77, 11, 2017.11, [URL], Observables sensitive to the anomalous production of events containing hadronic jets and missing momentum in the plane transverse to the proton beams at the Large Hadron Collider are presented. The observables are defined as a ratio of cross sections, for events containing jets and large missing transverse momentum to events containing jets and a pair of charged leptons from the decay of a Z/ γboson. This definition minimises experimental and theoretical systematic uncertainties in the measurements. This ratio is measured differentially with respect to a number of kinematic properties of the hadronic system in two phase-space regions; one inclusive single-jet region and one region sensitive to vector-boson-fusion topologies. The data are found to be in agreement with the Standard Model predictions and used to constrain a variety of theoretical models for dark-matter production, including simplified models, effective field theory models, and invisible decays of the Higgs boson. The measurements use 3.2 fb- 1of proton–proton collision data recorded by the ATLAS experiment at a centre-of-mass energy of 13 TeV and are fully corrected for detector effects, meaning that the data can be used to constrain new-physics models beyond those shown in this paper..
140. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of b-hadron pair production with the ATLAS detector in proton-proton collisions at √s=8 TeV, Journal of High Energy Physics, 10.1007/JHEP11(2017)062, 2017, 11, 2017.11, [URL], A measurement of b-hadron pair production is presented, based on a data set corresponding to an integrated luminosity of 11.4 fb−1 of proton-proton collisions recorded at s=8 TeV with the ATLAS detector at the LHC. Events are selected in which a b-hadron is reconstructed in a decay channel containing J/ψ → μμ, and a second b-hadron is reconstructed in a decay channel containing a muon. Results are presented in a fiducial volume defined by kinematic requirements on three muons based on those used in the analysis. The fiducial cross section is measured to be 17.7 ± 0.1(stat.) ± 2.0(syst.) nb. A number of normalised differential cross sections are also measured, and compared to predictions from the Pythia8, Herwig++, MadGraph5_aMC@NLO+Pythia8 and Sherpa event generators, providing new constraints on heavy flavour production.[Figure not available: see fulltext.]..
141. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, ATLAS Collaboration, Nuclear Physics A, 10.1016/S0375-9474(17)30376-7, 967, 942-964, 2017.11, [URL].
142. M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J.Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Study of the material of the ATLAS inner detector for Run 2 of the LHC, Journal of Instrumentation, 10.1088/1748-0221/12/12/P12009, 12, 12, 2017.12, [URL], The ATLAS inner detector comprises three different sub-detectors: the pixel detector, the silicon strip tracker, and the transition-radiation drift-tube tracker. The Insertable B-Layer, a new innermost pixel layer, was installed during the shutdown period in 2014, together with modifications to the layout of the cables and support structures of the existing pixel detector. The material in the inner detector is studied with several methods, using a low-luminosity s=13 TeV pp collision sample corresponding to around 2.0 nb-1 collected in 2015 with the ATLAS experiment at the LHC. In this paper, the material within the innermost barrel region is studied using reconstructed hadronic interaction and photon conversion vertices. For the forward rapidity region, the material is probed by a measurement of the efficiency with which single tracks reconstructed from pixel detector hits alone can be extended with hits on the track in the strip layers. The results of these studies have been taken into account in an improved description of the material in the ATLAS inner detector simulation, resulting in a reduction in the uncertainties associated with the charged-particle reconstruction efficiency determined from simulation..
143. M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Search for squarks and gluinos in events with an isolated lepton, jets, and missing transverse momentum at √s=13 TeV with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.96.112010, 96, 11, 2017.12, [URL], The results of a search for squarks and gluinos in final states with an isolated electron or muon, multiple jets and large missing transverse momentum using proton-proton collision data at a center-of-mass energy of √ = 13 TeV are presented. The data set used was recorded during 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 36.1 fb-1. No significant excess beyond the expected background is found. Exclusion limits at 95% confidence level are set in a number of supersymmetric scenarios, reaching masses up to 2.1 TeV for gluino pair production and up to 1.25 TeV for squark pair production..
144. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for new phenomena with large jet multiplicities and missing transverse momentum using large-radius jets and flavour-tagging at ATLAS in 13 TeV pp collisions, Journal of High Energy Physics, 10.1007/JHEP12(2017)034, 2017, 12, 2017.12, [URL], A search is presented for particles that decay producing a large jet multiplicity and invisible particles. The event selection applies a veto on the presence of isolated electrons or muons and additional requirements on the number of b-tagged jets and the scalar sum of masses of large-radius jets. Having explored the full ATLAS 2015-2016 dataset of LHC proton-proton collisions at s=13 TeV, which corresponds to 36.1 fb−1 of integrated luminosity, no evidence is found for physics beyond the Standard Model. The results are interpreted in the context of simplified models inspired by R-parity-conserving and R-parity-violating supersymmetry, where gluinos are pair-produced. More generic models within the phenomenological minimal supersymmetric Standard Model are also considered..
145. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for new phenomena in high-mass diphoton final states using 37 fb−1 of proton–proton collisions collected at s=13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2017.10.039, 775, 105-125, 2017.12, [URL], Searches for new phenomena in high-mass diphoton final states with the ATLAS experiment at the LHC are presented. The analysis is based on pp collision data corresponding to an integrated luminosity of 36.7 fb−1 at a centre-of-mass energy s=13 TeV recorded in 2015 and 2016. Searches are performed for resonances with spin 0, as predicted by theories with an extended Higgs sector, and for resonances with spin 2, using a warped extra-dimension model as a benchmark model, as well as for non-resonant signals, assuming a large extra-dimension scenario. No significant deviation from the Standard Model is observed. Upper limits are placed on the production cross section times branching ratio to two photons as a function of the resonance mass. In addition, lower limits are set on the ultraviolet cutoff scale in the large extra-dimensions model..
146. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. AlconadaVerzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for direct top squark pair production in final states with two leptons in √s=13 TeV pp collisions with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-5445-x, 77, 12, 2017.12, [URL], The results of a search for direct pair production of top squarks in events with two opposite-charge leptons (electrons or muons) are reported, using 36.1fb-1 of integrated luminosity from proton–proton collisions at s=13 TeV collected by the ATLAS detector at the Large Hadron Collider. To cover a range of mass differences between the top squark t~ and lighter supersymmetric particles, four possible decay modes of the top squark are targeted with dedicated selections: the decay t~→bχ~1± into a b-quark and the lightest chargino with χ~1±→Wχ~10, the decay t~→tχ~10 into an on-shell top quark and the lightest neutralino, the three-body decay t~→bWχ~10 and the four-body decay t~→b10. No significant excess of events is observed above the Standard Model background for any selection, and limits on top squarks are set as a function of the t~ and χ~10 masses. The results exclude at 95% confidence level t~ masses up to about 720 GeV, extending the exclusion region of supersymmetric parameter space covered by previous searches..
147. M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Search for dark matter in association with a Higgs boson decaying to two photons at √s=13 TeV with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.96.112004, 96, 11, 2017.12, [URL], A search for dark matter in association with a Higgs boson decaying to two photons is presented. This study is based on data collected with the ATLAS detector, corresponding to an integrated luminosity of 36.1 fb-1 of proton-proton collisions at the LHC at a center-of-mass energy of 13 TeV in 2015 and 2016. No significant excess over the expected background is observed. Upper limits at 95% confidence level are set on the visible cross section for beyond the Standard Model physics processes, and the production cross section times branching fraction of the Standard Model Higgs boson decaying into two photons in association with missing transverse momentum in three different benchmark models. Limits at 95% confidence level are also set on the observed signal in two-dimensional mass planes. Additionally, the results are interpreted in terms of 90% confidence-level limits on the dark-matter-nucleon scattering cross section, as a function of the dark-matter particle mass, for a spin-independent scenario..
148. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for a scalar partner of the top quark in the jets plus missing transverse momentum final state at √s=13 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP12(2017)085, 2017, 12, 2017.12, [URL], A search for pair production of a scalar partner of the top quark in events with four or more jets plus missing transverse momentum is presented. An analysis of 36.1 fb−1 of s=13 TeV proton-proton collisions collected using the ATLAS detector at the LHC yields no significant excess over the expected Standard Model background. To interpret the results a simplified supersymmetric model is used where the top squark is assumed to decay via t˜1→t(∗)χ˜10 and t˜1→bχ˜1±→bW(∗)χ˜10, where χ1 01 ±) denotes the lightest neutralino (chargino). Exclusion limits are placed in terms of the top-squark and neutralino masses. Assuming a branching ratio of 100% to tχ˜10, top-squark masses in the range 450–1000 GeV are excluded for χ˜10 masses below 160 GeV. In the case where mt˜1∼mt+mχ˜10, top-squark masses in the range 235–590 GeV are excluded..
149. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of the cross-section for electroweak production of dijets in association with a Z boson in pp collisions at s=13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2017.10.040, 775, 206-228, 2017.12, [URL], The cross-section for the production of two jets in association with a leptonically decaying Z boson (Zjj) is measured in proton–proton collisions at a centre-of-mass energy of 13 TeV, using data recorded with the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 3.2 fb−1. The electroweak Zjj cross-section is extracted in a fiducial region chosen to enhance the electroweak contribution relative to the dominant Drell–Yan Zjj process, which is constrained using a data-driven approach. The measured fiducial electroweak cross-section is σEW Zjj = 119±16(stat.)±20(syst.)±2(lumi.) fb for dijet invariant mass greater than 250 GeV, and 34.2±5.8(stat.)±5.5(syst.)±0.7(lumi.) fb for dijet invariant mass greater than 1 TeV. Standard Model predictions are in agreement with the measurements. The inclusive Zjj cross-section is also measured in six different fiducial regions with varying contributions from electroweak and Drell–Yan Zjj production..
150. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of the Drell-Yan triple-differential cross section in pp collisions at √s=8 TeV, Journal of High Energy Physics, 10.1007/JHEP12(2017)059, 2017, 12, 2017.12, [URL], This paper presents a measurement of the triple-differential cross section for the Drell-Yan process Z/γ* → ℓ+ where ℓ is an electron or a muon. The measurement is performed for invariant masses of the lepton pairs, mℓℓ, between 46 and 200 GeV using a sample of 20.2 fb−1 of pp collisions data at a centre-of-mass energy of s=8 TeV collected by the ATLAS detector at the LHC in 2012. The data are presented in bins of invariant mass, absolute dilepton rapidity, |yℓℓ|, and the angular variable cos θ* between the outgoing lepton and the incoming quark in the Collins-Soper frame. The measurements are performed in the range |yℓℓ| < 2.4 in the muon channel, and extended to |yℓℓ| < 3.6 in the electron channel. The cross sections are used to determine the Z boson forward-backward asymmetry as a function of |yℓℓ| and mℓℓ. The measurements achieve high-precision, below the percent level in the pole region, excluding the uncertainty in the integrated luminosity, and are in agreement with predictions. These precision data are sensitive to the parton distribution functions and the effective weak mixing angle..
151. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. Agricola, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Femtoscopy with identified charged pions in proton-lead collisions at s NN =5.02 TeV with ATLAS, Physical Review C, 10.1103/PhysRevC.96.064908, 96, 6, 2017.12, [URL], Bose-Einstein correlations between identified charged pions are measured for p+Pb collisions at sNN=5.02TeV using data recorded by the ATLAS detector at the CERN Large Hadron Collider corresponding to a total integrated luminosity of 28nb-1. Pions are identified using ionization energy loss measured in the pixel detector. Two-particle correlation functions and the extracted source radii are presented as a function of collision centrality as well as the average transverse momentum (kT) and rapidity (yππ) of the pair. Pairs are selected with a rapidity -2
152. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Evidence for the H → bb decay with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP12(2017)024, 2017, 12, 1-69, 2017.12, [URL], A search for the decay of the Standard Model Higgs boson into a bb pair when produced in association with a W or Z boson is performed with the ATLAS detector. The analysed data, corresponding to an integrated luminosity of 36.1 fb-1, were collected in proton-proton collisions in Run 2 of the Large Hadron Collider at a centre-of-mass energy of 13TeV. Final states containing zero, one and two charged leptons (electrons or muons) are considered, targeting the decays Z → νν, W → ℓν and Z → ℓℓ. For a Higgs boson mass of 125 GeV, an excess of events over the expected background from other Standard Model processes is found with an observed significance of 3.5 standard deviations, compared to an expectation of 3.0 standard deviations. This excess provides evidence for the Higgs boson decay into b-quarks and for its production in association with a vector boson. The combination of this result with that of the Run 1 analysis yields a ratio of the measured signal events to the Standard Model expectation equal to 0.90 ± 0.18(stat.)+0.21 -0.19(syst.). Assuming the Standard Model production cross-section, the results are consistent with the value of the Yukawa coupling to b-quarks in the Standard Model..
153. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Analysis of the Wtb vertex from the measurement of triple-differential angular decay rates of single top quarks produced in the t-channel at √s=8 TeV with the ATLAS detector, Journal of High Energy Physics, 10.1007/JHEP12(2017)017, 2017, 12, 2017.12, [URL], The electroweak production and subsequent decay of single top quarks in the t-channel is determined by the properties of the Wtb vertex, which can be described by the complex parameters of an effective Lagrangian. An analysis of a triple-differential decay rate in t-channel production is used to simultaneously determine five generalised helicity fractions and phases, as well as the polarisation of the produced top quark. The complex parameters are then constrained. This analysis is based on 20.2 fb−1 of proton-proton collision data at a centre-of-mass energy of 8 TeV collected with the ATLAS detector at the LHC. The fraction of decays containing transversely polarised W bosons is measured to be f1 = 0.30 ± 0.05. The phase between amplitudes for transversely and longitudinally polarised W bosons recoiling against left-handed b-quarks is measured to be δ = 0.002π+ 0.017π + 0.016π, giving no indication of CP violation. The fractions of longitudinal or transverse W bosons accompanied by right-handed b-quarks are also constrained. Based on these measurements, limits are placed at 95% CL on the ratio of the complex coupling parameters Re [gR/VL ∈ [−0.12, 0.17] and Im [gR/VL ∈ [−0.07, 0.06]. Constraints are also placed on the ratios |VR/VL| and |gL/VL|. In addition, the polarisation of single top quarks in the t-channel is constrained to be P > 0.72 (95% CL). None of the above measurements make assumptions about the value of any of the other parameters or couplings and all of them are in agreement with the Standard Model.[Figure not available: see fulltext.]..
154. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for heavy resonances decaying into WW in the e final state in pp collisions at √s=13TeV with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-5491-4, 78, 1, 2018.01, [URL], A search for neutral heavy resonances is performed in the WW→ e decay channel using pp collision data corresponding to an integrated luminosity of 36.1fb-1, collected at a centre-of-mass energy of 13TeV by the ATLAS detector at the Large Hadron Collider. No evidence of such heavy resonances is found. In the search for production via the quark–antiquark annihilation or gluon–gluon fusion process, upper limits on σX× B(X→ WW) as a function of the resonance mass are obtained in the mass range between 200GeV and up to 5TeV for various benchmark models: a Higgs-like scalar in different width scenarios, a two-Higgs-doublet model, a heavy vector triplet model, and a warped extra dimensions model. In the vector-boson fusion process, constraints are also obtained on these resonances, as well as on a Higgs boson in the Georgi–Machacek model and a heavy tensor particle coupling only to gauge bosons..
155. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for dark matter produced in association with bottom or top quarks in √s=13 TeV pp collisions with the ATLAS detector, European Physical Journal C, 10.1140/epjc/s10052-017-5486-1, 78, 1, 2018.01, [URL], A search for weakly interacting massive dark-matter particles produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and missing transverse momentum are considered. The analysis uses 36.1fb-1 of proton–proton collision data recorded by the ATLAS experiment at s=13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are interpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour-neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross-section of 300 times the predicted rate for mediators with masses between 10 and 50GeV and assuming a dark-matter mass of 1GeV and unitary coupling. Constraints on colour-charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35GeV, mediator particles with mass below 1.1TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements..
156. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a Z boson in pp collisions at s=13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2017.11.049, 776, 318-337, 2018.01, [URL], A search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a leptonically decaying Z boson in proton–proton collisions at s=13 TeV is presented. This search uses 36.1 fb−1 of data collected by the ATLAS experiment at the Large Hadron Collider. No significant deviation from the expectation of the Standard Model backgrounds is observed. Assuming the Standard Model ZH production cross-section, an observed (expected) upper limit of 67% (39%) at the 95% confidence level is set on the branching ratio of invisible decays of the Higgs boson with mass mH=125 GeV. The corresponding limits on the production cross-section of the ZH process with the invisible Higgs boson decays are also presented. Furthermore, exclusion limits on the dark matter candidate and mediator masses are reported in the framework of simplified dark matter models..
157. , M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B. Abeloos, R. Aben, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, D. L. Adams, J. Adelman, S. Adomeit, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, H. Akerstedt, Åkesson T. P.A., A. V. Akimov, G. L. Alberghi, J. Albert, S. Albrand, M. J. Alconada Verzini, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, P. P. Allport, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of the cross-section for producing a W boson in association with a single top quark in pp collisions at √s=13 TeV with ATLAS, Journal of High Energy Physics, 10.1007/JHEP01(2018)063, 2018, 1, 2018.01, [URL], The inclusive cross-section for the associated production of a W boson and top quark is measured using data from proton-proton collisions at s=13 TeV. The dataset corresponds to an integrated luminosity of 3.2 fb−1, and was collected in 2015 by the ATLAS detector at the Large Hadron Collider at CERN. Events are selected requiring two opposite sign isolated leptons and at least one jet; they are separated into signal and control regions based on their jet multiplicity and the number of jets that are identified as containing b hadrons. The W t signal is then separated from the tt¯ background using boosted decision tree discriminants in two regions. The cross-section is extracted by fitting templates to the data distributions, and is measured to be σW t = 94 ± 10(stat.)− 22 + 28(syst.) ± 2(lumi.) pb. The measured value is in good agreement with the SM prediction of σtheory = 71.7±1.8 (scale)± 3.4 (PDF) pb [1].[Figure not available: see fulltext.]..
158. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of differential cross sections of isolated-photon plus heavy-flavour jet production in pp collisions at s=8 TeV using the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2017.11.054, 776, 295-317, 2018.01, [URL], This Letter presents the measurement of differential cross sections of isolated prompt photons produced in association with a b-jet or a c-jet. These final states provide sensitivity to the heavy-flavour content of the proton and aspects related to the modelling of heavy-flavour quarks in perturbative QCD. The measurement uses proton–proton collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of up to 20.2 fb−1. The differential cross sections are measured for each jet flavour with respect to the transverse energy of the leading photon in two photon pseudorapidity regions: |ηγ|<1.37 and 1.56<|ηγ|<2.37. The measurement covers photon transverse energies 25T γ<400 GeV and 25T γ<350 GeV respectively for the two |ηγ| regions. For each jet flavour, the ratio of the cross sections in the two |ηγ| regions is also measured. The measurement is corrected for detector effects and compared to leading-order and next-to-leading-order perturbative QCD calculations, based on various treatments and assumptions about the heavy-flavour content of the proton. Overall, the predictions agree well with the measurement, but some deviations are observed at high photon transverse energies. The total uncertainty in the measurement ranges between 13% and 66%, while the central γ+b measurement exhibits the smallest uncertainty, ranging from 13% to 27%, which is comparable to the precision of the theoretical predictions..
159. M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. AdamczyK, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. AfiK, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Z Z → + - ′ + ′ - s-section measurements and search for anomalous triple gauge couplings in 13 TeV p p collisions with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.97.032005, 97, 3, 2018.02, [URL], Measurements of ZZ production in the +-′+′- channel in proton-proton collisions at 13 TeV center-of-mass energy at the Large Hadron Collider are presented. The data correspond to 36.1 fb-1 of collisions collected by the ATLAS experiment in 2015 and 2016. Here and ′ stand for electrons or muons. Integrated and differential ZZ→+-′+′- cross sections with Z→+- candidate masses in the range of 66 GeV to 116 GeV are measured in a fiducial phase space corresponding to the detector acceptance and corrected for detector effects. The differential cross sections are presented in bins of twenty observables, including several that describe the jet activity. The integrated cross section is also extrapolated to a total phase space and to all standard model decays of Z bosons with mass between 66 GeV and 116 GeV, resulting in a value of 17.3±0.9[±0.6(stat)±0.5(syst)±0.6(lumi)] pb. The measurements are found to be in good agreement with the standard model. A search for neutral triple gauge couplings is performed using the transverse momentum distribution of the leading Z boson candidate. No evidence for such couplings is found and exclusion limits are set on their parameters..
160. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for diboson resonances with boson-tagged jets in pp collisions at s=13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2017.12.011, 777, 91-113, 2018.02, [URL], Narrow resonances decaying into WW, WZ or ZZ boson pairs are searched for in 36.7 fb−1 of proton–proton collision data at a centre-of-mass energy of s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. The diboson system is reconstructed using pairs of large-radius jets with high transverse momentum and tagged as compatible with the hadronic decay of high-momentum W or Z bosons, using jet mass and substructure properties. The search is sensitive to diboson resonances with masses in the range 1.2–5.0 TeV. No significant excess is observed in any signal region. Exclusion limits are set at the 95% confidence level on the production cross section times branching ratio to dibosons for a range of theories beyond the Standard Model. Model-dependent lower limits on the mass of new gauge bosons are set, with the highest limit set at 3.5 TeV in the context of mass-degenerate resonances that couple predominantly to bosons..
161. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of the exclusive γγ → μ+μ process in proton–proton collisions at s=13TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2017.12.043, 777, 303-323, 2018.02, [URL], The production of exclusive γγ→μ+μ events in proton–proton collisions at a centre-of-mass energy of 13 TeV is measured with the ATLAS detector at the LHC, using data corresponding to an integrated luminosity of 3.2 fb−1. The measurement is performed for a dimuon invariant mass of 12GeVμ+μ <70GeV. The integrated cross-section is determined within a fiducial acceptance region of the ATLAS detector and differential cross-sections are measured as a function of the dimuon invariant mass. The results are compared to theoretical predictions both with and without corrections for absorptive effects..
162. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, B. M.M. Allbrooke, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for long-lived, massive particles in events with displaced vertices and missing transverse momentum in s =13 TeV pp collisions with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.97.052012, 97, 5, 2018.03, [URL], A search for long-lived, massive particles predicted by many theories beyond the Standard Model is presented. The search targets final states with large missing transverse momentum and at least one high-mass displaced vertex with five or more tracks, and uses 32.8 fb-1 of s=13 TeV pp collision data collected by the ATLAS detector at the LHC. The observed yield is consistent with the expected background. The results are used to extract 95% C.L. exclusion limits on the production of long-lived gluinos with masses up to 2.37 TeV and lifetimes of O(10-2)-O(10) ns in a simplified model inspired by split supersymmetry..
163. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. Abouzeid, N. L. Abraham, H. Abramowicz, H. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, C. Allaire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Search for electroweak production of supersymmetric states in scenarios with compressed mass spectra at s =13 TeV with the ATLAS detector, Physical Review D, 10.1103/PhysRevD.97.052010, 97, 5, 2018.03, [URL], A search for electroweak production of supersymmetric particles in scenarios with compressed mass spectra in final states with two low-momentum leptons and missing transverse momentum is presented. This search uses proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015-2016, corresponding to 36.1 fb-1 of integrated luminosity at s=13 TeV. Events with same-flavor pairs of electrons or muons with opposite electric charge are selected. The data are found to be consistent with the Standard Model prediction. Results are interpreted using simplified models of R-parity-conserving supersymmetry in which there is a small mass difference between the masses of the produced supersymmetric particles and the lightest neutralino. Exclusion limits at 95% confidence level are set on next-to-lightest neutralino masses of up to 145 GeV for Higgsino production and 175 GeV for wino production, and slepton masses of up to 190 GeV for pair production of sleptons. In the compressed mass regime, the exclusion limits extend down to mass splittings of 2.5 GeV for Higgsino production, 2 GeV for wino production, and 1 GeV for slepton production. The results are also interpreted in the context of a radiatively-driven natural supersymmetry model with nonuniversal Higgs boson masses..
164. Taikan Suehara, I. Sekiya, S. Callier, V. Balagura, V. Boudry, J. C. Brient, C. De La Taille, Kiyotomo Kawagoe, A. Irles, F. Magniette, J. Nanni, R. Pöschl, T. Yoshioka, Performance study of SKIROC2/A ASIC for ILD Si-W ECAL, Journal of Instrumentation, 10.1088/1748-0221/13/03/C03015, 13, 3, 2018.03, [URL], The ILD Si-W ECAL is a sampling calorimeter with tungsten absorber and highly segmented silicon layers for the International Large Detector (ILD), one of the two detector concepts for the International Linear Collider. SKIROC2 is an ASIC for the ILD Si-W ECAL. To investigate the issues found in prototype detectors, we prepared dedicated ASIC evaluation boards with either BGA sockets or directly soldered SKIROC2. We report a performance study with the evaluation boards, including signal-to-noise ratio and TDC performance with comparing SKIROC2 and an updated version, SKIROC2A..
165. , J. Repond, L. Xia, G. Eigen, T. Price, N. K. Watson, A. Winter, M. A. Thomson, C. Cârloganu, G. C. Blazey, A. Dyshkant, K. Francis, V. Zutshi, K. Gadow, P. Göttlicher, O. Hartbrich, K. Kotera, F. Krivan, K. Krüger, S. Lu, B. Lutz, M. Reinecke, F. Sefkow, Y. Sudo, H. L. Tran, A. Kaplan, H. Ch Schultz-Coulon, B. Bilki, D. Northacker, Y. Onel, G. W. Wilson, K. Kawagoe, Kiyotomo Kawagoe, T. Suehara, Taikan Suehara, T. Yoshioka, E. Calvo Alamillo, M. C. Fouz, J. Marin, J. Navarrete, J. Puerta Pelayo, A. Verdugo, M. Chadeeva, M. Danilov, M. Gabriel, P. Goecke, C. Graf, Y. Israeli, N. van der Kolk, F. Simon, M. Szalay, Construction and response of a highly granular scintillator-based electromagnetic calorimeter, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 10.1016/j.nima.2018.01.016, 887, 150-168, 2018.04, [URL], A highly granular electromagnetic calorimeter with scintillator strip readout is being developed for future linear collider experiments. A prototype of 21.5 X0 depth and 180×180mm2 transverse dimensions was constructed, consisting of 2160 individually read out 10×45×3mm3 scintillator strips. This prototype was tested using electrons of 2–32 GeV at the Fermilab Test Beam Facility in 2009. Deviations from linear energy response were less than 1.1%, and the intrinsic energy resolution was determined to be (12.5±0.1(stat.)±0.4(syst.))%∕E[GeV]⊕(1.2±0.1(stat.)−0.7 +0.6(syst.))%, where the uncertainties correspond to statistical and systematic sources, respectively..
166. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, R. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, T. Agatonovic-Jovin, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, H. Akerstedt, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. C. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of the production cross-section of a single top quark in association with a Z boson in proton–proton collisions at 13 TeV with the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2018.03.023, 780, 557-577, 2018.05, [URL], The production of a top quark in association with a Z boson is investigated. The proton–proton collision data collected by the ATLAS experiment at the LHC in 2015 and 2016 at a centre-of-mass energy of s=13TeV are used, corresponding to an integrated luminosity of 36.1fb−1. Events containing three identified leptons (electrons and/or muons) and two jets, one of which is identified as a b-quark jet are selected. The major backgrounds are diboson, tt¯ and Z+jets production. A neural network is used to improve the background rejection and extract the signal. The resulting significance is 4.2σ in the data and the expected significance is 5.4σ. The measured cross-section for tZq production is 600±170(stat.)±140(syst.)fb..
167. , M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, Y. Abulaiti, B. S. Acharya, S. Adachi, L. Adamczyk, J. Adelman, M. Adersberger, T. Adye, A. A. Affolder, Y. Afik, C. Agheorghiesei, J. A. Aguilar-Saavedra, S. P. Ahlen, F. Ahmadov, G. Aielli, S. Akatsuka, Åkesson T. P.A., E. Akilli, A. V. Akimov, G. L. Alberghi, J. Albert, P. Albicocco, M. J. Alconada Verzini, S. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, G. Alexander, T. Alexopoulos, M. Alhroob, B. Ali, M. Aliev, G. Alimonti, J. Alison, S. P. Alkire, C. Allaire, B. M.M. Allbrooke, B. W. Allen, Kiyotomo Kawagoe, Hidetoshi Otono, Junji Tojo, Measurement of the production cross section of three isolated photons in pp collisions at s=8 TeV using the ATLAS detector, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 10.1016/j.physletb.2018.03.057, 781, 55-76, 2018.06, [URL], A measurement of the production of three isolated photons in proton–proton collisions at a centre-of-mass energy s=8 TeV is reported. The results are based on an integrated luminosity of 20.2 fb−1 collected with the ATLAS detector at the LHC. The differential cross sections are measured as functions of the transverse energy of each photon, the difference in azimuthal angle and in pseudorapidity between pairs of photons, the invariant mass of pairs of photons, and the invariant mass of the triphoton system. A measurement of the inclusive fiducial cross section is also reported. Next-to-leading-order perturbative QCD predictions are compared to the cross-section measurements. The predictions underestimate the measurement of the inclusive fiducial cross section and the differential measurements at low photon transverse energies and invariant masses. They provide adequate descriptions of the measurements at high values of the photon transverse energies, invariant mass of pairs of photons, and invariant mass of the triphoton system..
168. KIYOTOMO KAWAGOE, G. Moortgat Pick, Physics at the e+e− linear collider, The European Physical Journal C, 10.1140/epjc/s10052-015-3511-9, 75, 371, 2015.08, A comprehensive review of physics at an e+e− linear collider in the energy range of √s=92 GeV–3 TeV is presented in view of recent and expected LHC results, experiments from low-energy as well as astroparticle physics. .
169. KIYOTOMO KAWAGOE, FELIX SEFKOW, ANDY WHITE, ROMAN POESCHL, JOSE REPOND, Experimental tests of particle flow calorimetry, Review of Modern Physics, 10.1103/RevModPhys.88.015003, 88, 015033, 2016.02, Precision physics at future colliders requires highly granular calorimeters to support the particle flow approach for event reconstruction..
170. KIYOTOMO KAWAGOE, Taikan Suehara, DHCAL with Minimal Absorber: Measurements with Positrons, Journal of Instrumentation, 10.1088/1748-0221/11/05/P05008, 11, 05, P05008, 2016.05, In special tests, the active layers of the CALICE Digital Hadron Calorimeter prototype, the DHCAL, were exposed to low energy particle beams, without being interleaved by absorber plates. .
171. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for resonances in the mass distribution of jet pairs with one or two jets identified as b-jets in proton--proton collisions at √s=13 TeV with the ATLAS detector , Phys. Lett. B, 10.1016/j.physletb.2016.05.064, 759, 229-246, 2016.08, Searches for high-mass resonances in the dijet invariant mass spectrum with one or two jets identified as b-jets are performed using an integrated luminosity of 3.2 fb−1 of proton--proton collisions with a centre-of-mass energy of √s=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. No evidence of anomalous phenomena is observed in the data, which are used to exclude, at 95% credibility level, excited b∗ quarks with masses from 1.1 TeV to 2.1 TeV and leptophobic Z′ bosons with masses from 1.1 TeV to 1.5 TeV. Contributions of a Gaussian signal shape with effective cross sections ranging from approximately 0.4 to 0.001 pb are also excluded in the mass range 1.5--5.0 TeV. .
172. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Charged-particle distributions in √s=13 TeV pp interactions measured with the ATLAS detector at the LHC , Phys. Lett. B, 10.1016/j.physletb.2016.04.050, 758, 67-88, 2016.07, Charged-particle distributions are measured in proton-proton collisions at a centre-of-mass energy of 13 TeV, using a data sample of nearly 9 million events, corresponding to an integrated luminosity of 170 μb−1, recorded by the ATLAS detector during a special Large Hadron Collider fill. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the dependence of the mean transverse momentum on the charged-particle multiplicity are presented. The measurements are performed with charged particles with transverse momentum greater than 500 MeV and absolute pseudorapidity less than 2.5, in events with at least one charged particle satisfying these kinematic requirements. Additional measurements in a reduced phase space with absolute pseudorapidity less than 0.8 are also presented, in order to compare with other experiments. The results are corrected for detector effects, presented as particle-level distributions and are compared to the predictions of various Monte Carlo event generators. .
173. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for single production of a vector-like quark via a heavy gluon in the 4b final state with the ATLAS detector in pp collisions at √s=8 TeV, Phys. Lett. B, 10.1016/j.physletb.2016.04.061, 758, 249-268, 2016.07, A search is performed for the process pp→G∗→BHb¯/B¯Hb→Hbb¯→bb¯bb¯, predicted in composite Higgs scenarios, where G∗ is a heavy colour octet vector resonance and BH a vector-like quark of charge −1/3. The data were obtained from pp collisions at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.5 fb−1, recorded by the ATLAS detector at the LHC. The largest background, multijet production, is estimated using a data-driven method. No significant excess of events with respect to Standard Model predictions is observed, and upper limits on the production cross section times branching ratio are set. Comparisons to the predictions from a specific benchmark model are made, resulting in lower mass limits in the two-dimensional mass plane of mG∗ vs. mBH. .
174. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of D∗±, D± and D±s meson production cross sections in pp collisions at √s=7 TeV with the ATLAS detector , Nucl. Phys. B, 10.1016/j.nuclphysb.2016.04.032, 907, 717-763, 2016.06, The production of D∗±, D± and D±s charmed mesons has been measured with the ATLAS detector in pp collisions at √s=7 TeV at the LHC, using data corresponding to an integrated luminosity of 280nb−1. The charmed mesons have been reconstructed in the range of transverse momentum 3.5
175. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A search for top squarks with R-parity-violating decays to all-hadronic final states with the ATLAS detector in √s = 8 TeV proton--proton collisions , JHEP, 10.1007/JHEP06(2016)067, 2016, 06, 067, 2016.06, A search for the pair production of top squarks, each with R-parity-violating decays into two Standard Model quarks, is performed using 17.4 fb−1 of √s = 8 TeV proton-proton collision data recorded by the ATLAS experiment at the LHC. Each top squark is assumed to decay to a b- and an s-quark, leading to four quarks in the final state. Background discrimination is achieved with the use of b-tagging and selections on the mass and substructure of large-radius jets, providing sensitivity to top squark masses as low as 100 GeV. No evidence of an excess beyond the Standard Model background prediction is observed and top squarks decaying to b¯s¯ are excluded for top squark masses in the range 100≤mt~≤315 GeV at 95% confidence level. .
176. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena in final states with large jet multiplicities and missing transverse momentum with ATLAS using √s=13 TeV proton--proton collisions , Phys. Lett. B, 10.1016/j.physletb.2016.04.005, 757, 334-355, 2016.06, Results are reported of a search for new phenomena, such as supersymmetric particle production, that could be observed in high-energy proton--proton collisions. Events with large numbers of jets, together with missing transverse momentum from unobserved particles, are selected. The data analysed were recorded by the ATLAS experiment during 2015 using the 13 TeV centre-of-mass proton--proton collisions at the Large Hadron Collider, and correspond to an integrated luminosity of 3.2 fb−1. The search selected events with various jet multiplicities from ≥7 to ≥10 jets, and with various b-jet multiplicity requirements to enhance sensitivity. No excess above Standard Model expectations is observed. The results are interpreted within two supersymmetry models, where gluino masses up to 1400 GeV are excluded at 95% confidence level, significantly extending previous limits. .
177. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena in events with a photon and missing transverse momentum in pp collisions at √s=13 TeV with the ATLAS detector , JHEP, 10.1007/JHEP06(2016)059, 2016, 06, 059, 2016.06, Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum with the ATLAS experiment at the Large Hadron Collider are reported. The data were collected in proton--proton collisions at a centre-of-mass energy of 13 TeV and correspond to an integrated luminosity of 3.2 fb−1. The observed data are in agreement with the Standard Model expectations. Exclusion limits are presented in models of new phenomena including pair production of dark matter candidates or large extra spatial dimensions. In a simplified model of dark matter and an axial-vector mediator, the search excludes mediator masses of up to 710 GeV for dark matter candidate masses up to 150 GeV. In an effective theory of dark matter production, values of the suppression scale M∗ up to 570 GeV are excluded and the effect of truncation for various coupling values is reported. For the ADD large extra spatial dimension model the search places more stringent limits than earlier searches in the same event topology, excluding MD up to about 2.3 (2.8) TeV for two (six) additional spatial dimensions; the limits are reduced by 20--40% depending on the number of additional spatial dimensions when applying a truncation procedure. .
178. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of Zγ and Zγγ production in pp collisions at √s= 8 TeV with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.93.112002, 93, 112002, 2016.06, The production of Z bosons with one or two isolated high-energy photons is studied using pp collisions at s√ = 8 TeV. The analyses use a data sample with an integrated luminosity of 20.3 fb−1 collected by the ATLAS detector during the 2012 LHC data taking. The Zγ and Zγγ production cross sections are measured with leptonic (e+e−, μ+μ−, νν¯) decays of the Z boson, in extended fiducial regions defined in terms of the lepton and photon acceptance. They are then compared to cross-section predictions from the Standard Model, where the sources of the photons are radiation off initial-state quarks and radiative Z-boson decay to charged leptons, and from fragmentation of final-state quarks and gluons into photons. The yields of events with photon transverse energy ET> 250 GeV from ℓ+ℓ−γ events and with ET> 400 GeV from νν¯γ events are used to search for anomalous triple gauge-boson couplings ZZγ and Zγγ. The yields of events with diphoton invariant mass mγγ> 200 GeV from ℓ+ℓ−γγ events and with mγγ> 300 GeV from νν¯γγ events are used to search for anomalous quartic gauge-boson couplings ZZγγ and Zγγγ. No deviations from Standard Model predictions are observed and limits are placed on parameters used to describe anomalous triple and quartic gauge-boson couplings. .
179. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Evidence for single top-quark production in the s-channel in proton-proton collisions at √s=8 TeV with the ATLAS detector using the Matrix Element Method , Phys. Lett. B, 10.1016/j.physletb.2016.03.017, 756, 228-246, 2016.05, This Letter presents evidence for single top-quark production in the s-channel using proton-proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS detector at the CERN Large Hadron Collider. The analysis is performed on events containing one isolated electron or muon, large missing transverse momentum and exactly two b-tagged jets in the final state. The analysed data set corresponds to an integrated luminosity of 20.3 fb−1. The signal is extracted using a maximum-likelihood fit of a discriminant which is based on the matrix element method and optimized in order to separate single-top-quark s-channel events from the main background contributions, which are top-quark pair production and W boson production in association with heavy-flavour jets. The measurement leads to an observed signal significance of 3.2 standard deviations and a measured cross-section of σs=4.8±0.8(stat.)+1.6−1.3(syst.) pb, which is consistent with the Standard Model expectation. The expected significance for the analysis is 3.9 standard deviations. .
180. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Standard Model Higgs boson produced in association with a vector boson and decaying into a tau pair in pp collisions at √s=8TeV with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.93.092005, 93, 092005, 2016.05, A search for the Standard Model Higgs boson produced in association with a vector boson with the decay H→ττ is presented. The data correspond to 20.3 fb−1 of integrated luminosity from proton-proton collisions at s√=8 TeV recorded by the ATLAS experiment at the LHC during 2012. The data agree with the background expectation, and 95% confidence-level upper limits are placed on the cross section of this process. The observed (expected) limit, expressed in terms of the signal strength μ=σ/σSM for mH=125GeV, is μ< 5.6 (3.7). The measured value of the signal strength is μ=2.3±1.6. .
181. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the dependence of transverse energy production at large pseudorapidity on the hard-scattering kinematics of proton--proton collisions at √s=2.76 TeV with ATLAS , Phys. Lett. B, 10.1016/j.physletb.2016.02.056, 756, 10-28, 2016.05, The relationship between jet production in the central region and the underlying-event activity in a pseudorapidity-separated region is studied in 4.0 pb−1 of √s=2.76 TeV pp collision data recorded with the ATLAS detector at the LHC. The underlying event is characterised through measurements of the average value of the sum of the transverse energy at large pseudorapidity downstream of one of the protons, which are reported here as a function of hard-scattering kinematic variables. The hard scattering is characterised by the average transverse momentum and pseudorapidity of the two highest transverse momentum jets in the event. The dijet kinematics are used to estimate, on an event-by-event basis, the scaled longitudinal momenta of the hard-scattered partons in the target and projectile beam-protons moving toward and away from the region measuring transverse energy, respectively. Transverse energy production at large pseudorapidity is observed to decrease with a linear dependence on the longitudinal momentum fraction in the target proton and to depend only weakly on that in the projectile proton. The results are compared to the predictions of various Monte Carlo event generators, which qualitatively reproduce the trends observed in data but generally underpredict the overall level of transverse energy at forward pseudorapidity. .
182. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the transverse momentum and ϕ∗η distributions of Drell--Yan lepton pairs in proton--proton collisions at √s=8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-016-4070-4, 76, 291, 2016.05, Distributions of transverse momentum pllT and the angular variable ϕ∗η of Drell--Yan lepton pairs are measured in 20.3 fb−1 of proton--proton collisions at √s=8 TeV with the ATLAS detector at the LHC. Measurements in electron-pair and muon-pair final states are corrected for detector effects and combined. Compared to previous measurements in proton--proton collisions at s√=7 TeV, these new measurements benefit from a larger data sample and improved control of systematic uncertainties. Measurements are performed in bins of lepton-pair mass above, around and below the Z-boson mass peak. The data are compared to predictions from perturbative and resummed QCD calculations. For values of ϕ∗η<1 the predictions from the Monte Carlo generator ResBos are generally consistent with the data within the theoretical uncertainties. However, at larger values of ϕ∗η this is not generally the case. Monte Carlo generators based on the parton-shower approach are unable to describe the data over the full range of pllT and the fixed-order prediction of DYNNLO falls below the data at high values of pllT. ResBos and the parton-shower Monte Carlo generators provide a much better description of the evolution of the ϕ∗η and pllT distributions as a function of lepton-pair mass and rapidity. .
183. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the differential cross-sections of prompt and non-prompt production of J/ψ and ψ(2S) in pp collisi ons at √s=7 and 8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-016-4050-8, 76, 283, 2016.05, The production rates of prompt and non-prompt J/ψ and ψ(2S) mesons are measured using 2.1 fb−1 and 11.4 fb−1 of data collected with the ATLAS experiment at the LHC, in proton-proton collisions at √s=7 and 8 TeV respectively. Production cross-sections for both prompt and non-prompt production sources, ratios of ψ(2S) to J/ψ production, and fractions of non-prompt to inclusive production for J/ψ and ψ(2S) are measured double-differentially as a function of meson pT and rapidity. These measurements are made in a restricted fiducial volume and also corrected for geometrical acceptance after which they are compared to a variety of theoretical predictions. .
184. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the charge asymmetry in highly boosted top-quark pair production in √s= 8 TeV pp collision data collected by the ATLAS experiment , Phys. Lett. B, 10.1016/j.physletb.2016.02.055, 756, 52-71, 2016.05, In the pp→tt¯ process the angular distributions of top and anti-top quarks are expected to present a subtle difference, which could be enhanced by processes not included in the Standard Model. This Letter presents a measurement of the charge asymmetry in events where the top-quark pair is produced with a large invariant mass. The analysis is performed on 20.3 fb−1 of pp collision data at s√= 8 TeV collected by the ATLAS experiment at the LHC, using reconstruction techniques specifically designed for the decay topology of highly boosted top quarks. The charge asymmetry in a fiducial region with large invariant mass of the top-quark pair (mtt¯> 0.75 TeV) and an absolute rapidity difference of the top and anti-top quark candidates within −2 <|yt|−|yt¯|< 2 is measured to be 4.2 ± 3.2%, in agreement with the Standard Model prediction at next-to-leading order. A differential measurement in three tt¯ mass bins is also presented. .
185. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Reconstruction of hadronic decay products of tau leptons with the ATLAS experiment , Eur. Phys. J. C, 10.1140/epjc/s10052-016-4110-0, 76, 295, 2016.05, This paper presents a new method of reconstructing the individual charged and neutral hadrons in tau decays with the ATLAS detector. The reconstructed hadrons are used to classify the decay mode and to calculate the visible four-momentum of reconstructed tau candidates, significantly improving the resolution with respect to the calibration in the existing tau reconstruction. The performance of the reconstruction algorithm is optimised and evaluated using simulation and validated using samples of Z→ττ and Z(→μμ)+jets events selected from proton-proton collisions at a centre-of-mass energy √s=8 TeV, corresponding to an integrated luminosity of 5 fb−1. .
186. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for supersymmetry at √s=13 TeV in final states with jets and two same-sign leptons or three leptons with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-016-4095-8, 76, 259, 2016.05, A search for strongly produced supersymmetric particles is conducted using signatures involving multiple energetic jets and either two isolated leptons (e or μ) with the same electric charge or at least three isolated leptons. The search also utilises b-tagged jets, missing transverse momentum and other observables to extend its sensitivity. The analysis uses a data sample of proton-proton collisions at √s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015 corresponding to a total integrated luminosity of 3.2 fb−1. No significant excess over the Standard Model expectation is observed. The results are interpreted in several simplified supersymmetric models and extend the exclusion limits from previous searches. In the context of exclusive production and simplified decay modes, gluino masses are excluded at 95% confidence level up to 1.1-1.3 TeV for light neutralinos (depending on the decay channel), and bottom squark masses are also excluded up to 540 GeV. In the former scenarios, neutralino masses are also excluded up to 550-850 GeV for gluino masses around 1 TeV. .
187. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of W±Z production cross sections in pp collisions at √s=8 TeV with the ATLAS detector and limits on anomalous gauge boson self-couplings , Phys. Rev. D, 10.1103/PhysRevD.93.092004, 93, 092004, 2016.05, This paper presents measurements of W±Z production in pp collisions at a center-of-mass energy of 8 TeV. The gauge bosons are reconstructed using their leptonic decay modes into electrons and muons. The data were collected in 2012 by the ATLAS experiment at the Large Hadron Collider, and correspond to an integrated luminosity of 20.3 fb−1. The measured inclusive cross section in the detector fiducial region is σW±Z→ℓ′ν ℓℓ=35.1± 0.9 (stat.) ±0.8 (sys.) ±0.8 (lumi.) fb, for one leptonic decay channel. In comparison, the next-to-leading-order Standard Model expectation is 30.0 ± 2.1 fb. Cross sections for W+Z and W−Z production and their ratio are presented as well as differential cross sections for several kinematic observables. Limits on anomalous triple gauge boson couplings are derived from the transverse mass spectrum of the W±Z system. From the analysis of events with a W and a Z boson associated with two or more forward jets an upper limit at 95% confidence level on the W±Z scattering cross section of 0.63 fb, for each leptonic decay channel, is established, while the Standard Model prediction at next-to-leading order is 0.13 fb. Limits on anomalous quartic gauge boson couplings are also extracted. .
188. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Muon reconstruction performance of the ATLAS detector in proton--proton collision data at √s=13 TeV, Eur. Phys. J. C, 10.1140/epjc/s10052-016-4120-y, 76, 292, 2016.05, This article documents the performance of the ATLAS muon identification and reconstruction using the first LHC dataset recorded at √s = 13 TeV in 2015. Using a large sample of J/ψ→μμ and Z→μμ decays from 3.2 fb−1 of pp collision data, measurements of the reconstruction efficiency, as well as of the momentum scale and resolution, are presented and compared to Monte Carlo simulations. The reconstruction efficiency is measured to be close to 99% over most of the covered phase space (|η|<2.5 and 52.2, the pT resolution for muons from Z→μμ decays is 2.9% while the precision of the momentum scale for low-pT muons from J/ψ→μμ decays is about 0.2%. .
189. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Beam-induced and cosmic-ray backgrounds observed in the ATLAS detector during the LHC 2012 proton-proton running period , JINST, 10.1088/1748-0221/11/05/P05013, 11, P05013, 2016.05, This paper discusses various observations on beam-induced and cosmic-ray backgrounds in the ATLAS detector during the LHC 2012 proton-proton run. Building on published results based on 2011 data, the correlations between background and residual pressure of the beam vacuum are revisited. Ghost charge evolution over 2012 and its role for backgrounds are evaluated. New methods to monitor ghost charge with beam-gas rates are presented and observations of LHC abort gap population by ghost charge are discussed in detail. Fake jets from colliding bunches and from ghost charge are analysed with improved methods, showing that ghost charge in individual radio-frequency buckets of the LHC can be resolved. Some results of two short periods of dedicated cosmic-ray background data-taking are shown; in particular cosmic-ray muon induced fake jet rates are compared to Monte Carlo simulations and to the fake jet rates from beam background. A thorough analysis of a particular LHC fill, where abnormally high background was observed, is presented. Correlations between backgrounds and beam intensity losses in special fills with very high β∗ are studied. .
190. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Standard Model Higgs boson decaying into bb¯ produced in association with top quarks decaying hadronically in pp collisions at √s=8 TeV with the ATLAS detector, JHEP, 10.1007/JHEP05(2016)160, 2016, 05, 160, 2016.05, A search for Higgs boson production in association with a pair of top quarks (tt¯H) is performed, where the Higgs boson decays to bb¯, and both top quarks decay hadronically. The data used correspond to an integrated luminosity of 20.3 fb−1 of pp collisions at √s=8 TeV collected with the ATLAS detector at the Large Hadron Collider. The search selects events with at least six energetic jets and uses a boosted decision tree algorithm to discriminate between signal and Standard Model background. The dominant multijet background is estimated using a dedicated data-driven technique. For a Higgs boson mass of 125 GeV, an upper limit of 6.4 (5.4) times the Standard Model cross section is observed (expected) at 95% confidence level. The best-fit value for the signal strength is μ=1.6±2.6 times the Standard Model expectation for mH=125 GeV. Combining all tt¯H searches carried out by ATLAS at √s=8 and 7 TeV, an observed (expected) upper limit of 3.1 (1.4) times the Standard Model expectation is obtained at 95% confidence level, with a signal strength μ=1.7±0.8. .
191. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the centrality dependence of the charged-particle pseudorapidity distribution in proton--lead collisions at √sNN=5.02 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-016-4002-3, 76, 199, 2016.04, The centrality dependence of the mean charged-particle multiplicity as a function of pseudorapidity is measured in approximately 1 μb−1 of proton--lead collisions at a nucleon--nucleon centre-of-mass energy of √sNN=5.02 TeV using the ATLAS detector at the Large Hadron Collider. Charged particles with absolute pseudorapidity less than 2.7 are reconstructed using the ATLAS pixel detector. The p+Pb collision centrality is characterised by the total transverse energy measured in the Pb-going direction of the forward calorimeter. The charged-particle pseudorapidity distributions are found to vary strongly with centrality, with an increasing asymmetry between the proton-going and Pb-going directions as the collisions become more central. Three different estimations of the number of nucleons participating in the p+Pb collision have been carried out using the Glauber model as well as two Glauber--Gribov inspired extensions to the Glauber model. Charged-particle multiplicities per participant pair are found to vary differently for these three models, highlighting the importance of including colour fluctuations in nucleon--nucleon collisions in the modelling of the initial state of p+Pb collisions. .
192. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Observation of long-range elliptic anisotropies in √s=13 and 2.76 TeV pp collisions with the ATLAS detector , Phys. Rev. Lett., 10.1103/PhysRevLett.116.172301, 116, 172301, 2016.04, ATLAS has measured two-particle correlations as a function of relative azimuthal-angle, Δϕ, and pseudorapidity, Δη, in √s=13 and 2.76 TeV pp collisions at the LHC using charged particles measured in the pseudorapidity interval |η|<2.5. The correlation functions evaluated in different intervals of measured charged-particle multiplicity show a multiplicity-dependent enhancement at Δϕ∼0 that extends over a wide range of Δη, which has been referred to as the "ridge". Per-trigger-particle yields, Y(Δϕ), are measured over 2<|Δη|<5. For both collision energies, the Y(Δϕ) distribution in all multiplicity intervals is found to be consistent with a linear combination of the per-trigger-particle yields measured in collisions with less than 20 reconstructed tracks, and a constant combinatoric contribution modulated by cos(2Δϕ). The fitted Fourier coefficient, v2,2, exhibits factorization, suggesting that the ridge results from per-event cos(2ϕ) modulation of the single-particle distribution with Fourier coefficients v2. The v2 values are presented as a function of multiplicity and transverse momentum. They are found to be approximately constant as a function of multiplicity and to have a pT dependence similar to that measured in p+Pb and Pb+Pb collisions. The v2 values in the 13 and 2.76 TeV data are consistent within uncertainties. These results suggest that the ridge in pp collisions arises from the same or similar underlying physics as observed in p+Pb collisions, and that the dynamics responsible for the ridge has no strong √s dependence. .
193. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A new method to distinguish hadronically decaying boosted Z bosons from W bosons using the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-016-4065-1, 76, 238, 2016.04, The distribution of particles inside hadronic jets produced in the decay of boosted W and Z bosons can be used to discriminate such jets from the continuum background. Given that a jet has been identified as likely resulting from the hadronic decay of a boosted W or Z boson, this paper presents a technique for further differentiating Z bosons from W bosons. The variables used are jet mass, jet charge, and a b-tagging discriminant. A likelihood tagger is constructed from these variables and tested in the simulation of W′→WZ for bosons in the transverse momentum range 200 GeV
194. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena in events with at least three photons collected in pp collisions at √s = 8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-016-4034-8, 76, 210, 2016.04, Results of a search for new phenomena in events with at least three photons are reported. Data from proton--proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb−1, were collected with the ATLAS detector at the LHC. The observed data are well described by the Standard Model. Limits at the 95% confidence level on new phenomena are presented based on the rate of events in an inclusive signal region and a restricted signal region targeting the rare decay Z→3γ, as well as di-photon and tri-photon resonance searches. For a Standard Model Higgs boson decaying to four photons via a pair of intermediate pseudoscalar particles (a), limits are found to be σ×BR(h→aa)×BR(a→γγ)2<10−3σSM for 10 GeV 125 GeV, and for a Z′ decaying to three photons via Z′→a+γ→3γ. Additionally, the observed limit on the branching ratio of the Z boson decay to three photons is found to be BR(Z→3γ)<2.2×10−6, a result five times stronger than the previous result from LEP. .
195. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for anomalous couplings in the Wtb vertex from the measurement of double differential angular decay rates of single top quarks produced in the t-channel with the ATLAS detector , JHEP, 10.1007/JHEP04(2016)023, 2016, 04, 023, 2016.04, The electroweak production and subsequent decay of single top quarks is determined by the properties of the Wtb vertex. This vertex can be described by the complex parameters of an effective Lagrangian. An analysis of angular distributions of the decay products of single top quarks produced in the t-channel constrains these parameters simultaneously. The analysis described in this paper uses 4.6 fb−1 of proton-proton collision data at √s = 7 TeV collected with the ATLAS detector at the LHC.Two parameters are measured simultaneously in this analysis. The fraction f1 of decays containing transversely polarised W bosons is measured to be 0.37±0.07 (stat.⊕syst.). The phase δ− between amplitudes for transversely and longitudinally polarised W bosons recoiling against left-handed b-quarks is measured to be −0.14π±0.036π (stat.⊕syst.).The correlation in the measurement of these parameters is 0.15. These values result in two-dimensional limits at the 95% confidence level on the ratio of the complex coupling parameters gR and VL, yielding Re [gR/VL] ∈[−0.36,0.10] and Im [gR/VL] ∈[−0.17,0.23] with a correlation of 0.11. The results are in good agreement with the predictions of the Standard Model. .
196. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for dark matter produced in association with a Higgs boson decaying to two bottom quarks in pp collisions at √s=8 TeV with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.93.072007, 93, 072007, 2016.04, This article reports on a search for dark matter pair production in association with a Higgs boson decaying to a pair of bottom quarks, using data from 20.3fb−1 of pp collisions at a center-of-mass energy of 8 TeV collected by the ATLAS detector at the LHC. The decay of the Higgs boson is reconstructed as a high-momentum bb¯ system with either a pair of small-radius jets, or a single large-radius jet with substructure. The observed data are found to be consistent with the expected Standard Model backgrounds. Model-independent upper limits are placed on the visible cross-sections for events with a Higgs boson decaying into bb¯ and large missing transverse momentum with thresholds ranging from 150 GeV to 400 GeV. Results are interpreted using a simplified model with a Z′ gauge boson decaying into different Higgs bosons predicted in a two-Higgs-doublet model, of which the heavy pseudoscalar Higgs decays into a pair of dark matter particles. Exclusion limits are also presented for the mass scales of various effective field theory operators that describe the interaction between dark matter particles and the Higgs boson. .
197. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Performance of b-Jet Identification in the ATLAS Experiment, JINST, 10.1088/1748-0221/11/04/P04008, 11, 04, P04008, 2016.04, The identification of jets containing b hadrons is important for the physics programme of the ATLAS experiment at the Large Hadron Collider. Several algorithms to identify jets containing b hadrons are described, ranging from those based on the reconstruction of an inclusive secondary vertex or the presence of tracks with large impact parameters to combined tagging algorithms making use of multi-variate discriminants. An independent b-tagging algorithm based on the reconstruction of muons inside jets as well as the b-tagging algorithm used in the online trigger are also presented.The b-jet tagging efficiency, the c-jet tagging efficiency and the mistag rate for light flavour jets in data have been measured with a number of complementary methods. The calibration results are presented as scale factors defined as the ratio of the efficiency (or mistag rate) in data to that in simulation. In the case of b jets, where more than one calibration method exists, the results from the various analyses have been combined taking into account the statistical correlation as well as the correlation of the sources of systematic uncertainty. .
198. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Combination of searches for WW, WZ, and ZZ resonances in pp collisions at √s=8 TeV with the ATLAS detector , Phys. Lett. B, 10.1016/j.physletb.2016.02.015, 755, 285-305, 2016.04, The ATLAS experiment at the CERN Large Hadron Collider has performed searches for new, heavy bosons decaying to WW, WZ and ZZ final states in multiple decay channels using 20.3 fb−1 of pp collision data at √s=8 TeV. In the current study, the results of these searches are combined to provide a more stringent test of models predicting heavy resonances with couplings to vector bosons. Direct searches for a charged diboson resonance decaying to WZ in the ℓνℓ′ℓ′ (ℓ=μ,e) , ℓℓqq¯, ℓνqq¯ and fully hadronic final states are combined and upper limits on the rate of production times branching ratio to the WZ bosons are compared with predictions of an extended gauge model with a heavy W′ boson. In addition, direct searches for a neutral diboson resonance decaying to WW and ZZ in the ℓℓqq¯, ℓνqq¯, and fully hadronic final states are combined and upper limits on the rate of production times branching ratio to the WW and ZZ bosons are compared with predictions for a heavy, spin-2 graviton in an extended Randall--Sundrum model where the Standard Model fields are allowed to propagate in the bulk of the extra dimension. .
199. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Probing lepton flavour violation via neutrinoless τ⟶3μ decays with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-016-4041-9, 76, 232, 2016.04, This article presents the sensitivity of the ATLAS experiment to the lepton-flavour-violating decays of τ→3μ. A method utilising the production of τ leptons via W→τν decays is used. This method is applied to the sample of 20.3 fb−1 of pp collision data at a centre-of-mass energy of 8 TeV collected by the ATLAS experiment at the LHC in 2012. No event is observed passing the selection criteria, and the observed (expected) upper limit on the τ lepton branching fraction into three muons, Br(τ→3μ), is 3.76×10−7 (3.94×10−7) at 90% confidence level. .
200. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Centrality, rapidity and transverse momentum dependence of isolated prompt photon production in lead-lead collisions at √sNN=2.76 TeV measured with the ATLAS detector, Phys. Rev. C, 10.1103/PhysRevC.93.034914, 93, 034914, 2016.03, Prompt photon production in √sNN=2.76 TeV Pb+Pb collisions has been measured by the ATLAS experiment at the Large Hadron Collider using data collected in 2011 with an integrated luminosity of 0.14 nb−1. Inclusive photon yields, scaled by the mean nuclear thickness function, are presented as a function of collision centrality and transverse momentum in two pseudorapidity intervals, |η|<1.37 and 1.52<|η|<2.37. The scaled yields in the two pseudorapidity intervals, as well as the ratios of the forward yields to those at midrapidity, are compared to the expectations from next-to-leading order perturbative QCD calculations from JETPHOX. The measured cross sections agree well with the predictions for proton-proton collisions within statistical and systematic uncertainties. Both the yields and ratios are also compared to two other pQCD calculations, one which uses the isospin content appropriate to colliding lead nuclei, and another which includes the EPS09 nuclear modifications to the nucleon parton distribution functions. .
201. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of jet charge in dijet events from √s=8 TeV pp collisions with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.93.052003, 93, 052003, 2016.03, The momentum-weighted sum of the charges of tracks associated to a jet is sensitive to the charge of the initiating quark or gluon. This paper presents a measurement of the distribution of momentum-weighted sums, called jet charge, in dijet events using 20.3 fb−1 of data recorded with the ATLAS detector at s√=8 TeV in pp collisions at the LHC. The jet charge distribution is unfolded to remove distortions from detector effects and the resulting particle-level distribution is compared with several models. The pT-dependence of the jet charge distribution average and standard deviation are compared to predictions obtained with several LO and NLO parton distribution functions. The data are also compared to different Monte Carlo simulations of QCD dijet production using various settings of the free parameters within these models. The chosen value of the strong coupling constant used to calculate gluon radiation is found to have a significant impact on the predicted jet charge. There is evidence for a pT-dependence of the jet charge distribution for a given jet flavor. In agreement with perturbative QCD predictions, the data show that the average jet charge of quark-initiated jets decreases in magnitude as the energy of the jet increases. .
202. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the electroweak production of supersymmetric particles in √s=8 TeV pp collisions with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.93.052002, 93, 052002, 2016.03, The ATLAS experiment has performed extensive searches for the electroweak production of charginos, neutralinos and staus. This article summarizes and extends the search for electroweak supersymmetry with new analyses targeting scenarios not covered by previously published searches. New searches use vector-boson fusion production, initial-state radiation jets, and low-momentum lepton final states, as well as multivariate analysis techniques to improve the sensitivity to scenarios with small mass splittings and low-production cross-sections. Results are based on 20 fb−1 of proton-proton collision data at √s=8 TeV recorded with the ATLAS experiment at the Large Hadron Collider. No significant excess beyond Standard Model expectations is observed. The new and existing searches are combined and interpreted in terms of 95% confidence-level exclusion limits in simplified models, where a single production process and decay mode is assumed, as well as within phenomenological supersymmetric models. .
203. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for magnetic monopoles and stable particles with high electric charges in 8 TeV pp collisions with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.93.052009, 93, 052009, 2016.03, A search for highly ionizing particles produced in proton-proton collisions at 8 TeV center-of-mass energy is performed by the ATLAS collaboration at the CERN Large Hadron Collider. The dataset used corresponds to an integrated luminosity of 7.0 fb−1. A customized trigger significantly increases the sensitivity, permitting a search for such particles with charges and energies beyond what was previously accessible. No events were found in the signal region, leading to production cross section upper limits in the mass range 200--2500 GeV for magnetic monopoles with magnetic charge in the range 0.5gD<|g|<2.0gD, where gD is the Dirac charge, and for stable particles with electric charge in the range 10<|z|<60. Model-dependent limits are presented in given pair-production scenarios, and model-independent limits are presented in fiducial regions of particle energy and pseudorapidity. .
204. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Identification of boosted, hadronically decaying W bosons and comparisons with ATLAS data taken at √s=8 TeV, Eur. Phys. J. C, 10.1140/epjc/s10052-016-3978-z, 76, 154, 2016.03, This paper reports a detailed study of techniques for identifying boosted, hadronically decaying W bosons using 20fb−1 of proton-proton collision data collected by the ATLAS detector at the LHC at a centre-of-mass energy √s= 8 TeV. A range of techniques for optimising the signal jet mass resolution are combined with various jet substructure variables. The results of these studies in Monte Carlo simulations show that a simple pairwise combination of groomed jet mass and one substructure variable can provide a 50% efficiency for identifying W bosons with transverse momenta larger than 200 GeV while maintaining multijet background efficiencies of 2-4% for jets with the same transverse momentum. These signal and background efficiencies are confirmed in data for a selection of tagging techniques. .
205. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Dijet production in √s=7 TeV pp collisions with large rapidity gaps at the ATLAS experiment , Phys. Lett. B, 10.1016/j.physletb.2016.01.028, 754, 214-234, 2016.03, A 6.8 nb−1 sample of pp collision data collected under low-luminosity conditions at s√=7 TeV by the ATLAS detector at the Large Hadron Collider is used to study diffractive dijet production. Events containing at least two jets with pT>20 GeV are selected and analysed in terms of variables which discriminate between diffractive and non-diffractive processes. Cross sections are measured differentially in ΔηF, the size of the observable forward region of pseudorapidity which is devoid of hadronic activity, and in an estimator, ξ~, of the fractional momentum loss of the proton assuming single diffractive dissociation (pp→pX). Model comparisons indicate a dominant non-diffractive contribution up to moderately large ΔηF and small ξ~, with a diffractive contribution which is significant at the highest ΔηF and the lowest ξ~. The rapidity-gap survival probability is estimated from comparisons of the data in this latter region with predictions based on diffractive parton distribution functions. .
206. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for New Phenomena in Dijet Mass and Angular Distributions from pp collisions at √s = 13 TeV with the ATLAS Detector, Phys. Lett. B, 10.1016/j.physletb.2016.01.032, 754, 302-322, 2016.03, This Letter describes a model-agnostic search for pairs of jets (dijets) produced by resonant and non-resonant phenomena beyond the Standard Model in 3.6 fb−1 of proton-proton collisions with a centre-of-mass energy of √s=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. The distribution of the invariant mass of the two leading jets is examined for local excesses above a data-derived estimate of the smoothly falling prediction of the Standard Model. The data are also compared to a Monte Carlo simulation of Standard Model angular distributions derived from the rapidity of the two jets. No evidence of anomalous phenomena is observed in the data, which are used to exclude, at 95% CL, quantum black holes with threshold masses below 8.3 TeV, 8.1 TeV, or 5.3 TeV in three different benchmark scenarios; resonance masses below 5.2 TeV for excited quarks, 2.6 TeV in a W′ model, a range of masses starting from mZ′=1.5 TeV and couplings from gq=0.2 in a Z′ model; and contact interactions with a compositeness scale below 12.0 TeV and 17.5 TeV respectively for destructive and constructive interference between the new interaction and QCD processes. These results significantly extend the ATLAS limits obtained from 8 TeV data. Gaussian-shaped contributions to the mass distribution are also excluded if the effective cross-section exceeds values ranging from approximately 50-300 fb for masses below 2 TeV to 2-20 fb for masses above 4 TeV. .
207. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for strong gravity in multijet final states produced in pp collisions at √s= 13 TeV using the ATLAS detector at the LHC , JHEP, 10.1007/JHEP03(2016)026, 2016, 03, 026, 2016.03, A search is conducted for new physics in multijet final states using 3.6 inverse femtobarns of data from proton-proton collisions at √s = 13 TeV taken at the CERN Large Hadron Collider with the ATLAS detector. Events are selected containing at least three jets with scalar sum of jet transverse momenta (HT) greater than 1 TeV. No excess is seen at large HT and limits are presented on new physics: models which produce final states containing at least three jets and having cross sections larger than 1.6 fb with HT > 5.8 TeV are excluded. Limits are also given in terms of new physics models of strong gravity that hypothesize additional space-time dimensions. .
208. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for charged Higgs bosons in the H±→tb decay channel in pp collisions at √s=8 TeV using the ATLAS detector , JHEP, 10.1007/JHEP03(2016)127, 2016, 03, 127, 2016.03, Charged Higgs bosons heavier than the top quark and decaying via H±→tb are searched for in proton--proton collisions measured with the ATLAS experiment at s√=8 TeV corresponding to an integrated luminosity of 20.3 fb−1. The production of a charged Higgs boson in association with a top quark, gb→tH±, is explored in the mass range 200 to 600 GeV using multi-jet final states with one electron or muon. In order to separate the signal from the Standard Model background, analysis techniques combining several kinematic variables are employed. An excess of events above the background-only hypothesis is observed across a wide mass range, amounting to up to 2.4 standard deviations. Upper limits are set on the gb→tH± production cross section times the branching fraction BR(H±→tb). Additionally, the complementary s-channel production, qq′→H±, is investigated through a reinterpretation of W′→tb searches in ATLAS. Final states with one electron or muon are relevant for H± masses from 0.4 to 2.0 TeV, whereas the all-hadronic final state covers the range 1.5 to 3.0 TeV. In these search channels, no significant excesses from the predictions of the Standard Model are observed, and upper limits are placed on the qq′→H± production cross section times the branching fraction BR(H±→tb). .
209. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the ZZ Production Cross Section in pp Collisions at √s=13 TeV with the ATLAS Detector , Phys. Rev. Lett., 10.1103/PhysRevLett.116.101801, 116, 101801, 2016.03, The ZZ production cross section in proton-proton collisions at 13 TeV center-of-mass energy is measured using 3.2 fb−1 of data recorded with the ATLAS detector at the Large Hadron Collider. The considered Z boson candidates decay to an electron or muon pair of mass 66-116 GeV. The cross section is measured in a fiducial phase space reflecting the detector acceptance. It is also extrapolated to a total phase space for Z bosons in the same mass range and of all decay modes, giving 16.7+2.2−2.0(stat.)+0.9−0.7(syst.)+1.0−0.7(lumi.) pb. The results agree with standard model predictions. .
210. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena with photon+jet events in proton-proton collisions at √s=13 TeV with the ATLAS detector , JHEP, 10.1007/JHEP03(2016)041, 2016, 03, 041, 2016.03, A search is performed for the production of high-mass resonances decaying into a photon and a jet in 3.2 fb−1 of proton--proton collisions at a centre-of-mass energy of √s=13 TeV collected by the ATLAS detector at the Large Hadron Collider. Selected events have an isolated photon and a jet, each with transverse momentum above 150 GeV. No significant deviation of the γ+jet invariant mass distribution from the background-only hypothesis is found. Limits are set at 95% confidence level on the cross sections of generic Gaussian-shaped signals and of a few benchmark phenomena beyond the Standard Model: excited quarks with vector-like couplings to the Standard Model particles, and non-thermal quantum black holes in two models of extra spatial dimensions. The minimum excluded visible cross sections for Gaussian-shaped resonances with width-to-mass ratios of 2% decrease from about 6 fb for a mass of 1.5 TeV to about 0.8 fb for a mass of 5 TeV. The minimum excluded visible cross sections for Gaussian-shaped resonances with width-to-mass ratios of 15% decrease from about 50 fb for a mass of 1.5 TeV to about 1.0 fb for a mass of 5 TeV. Excited quarks are excluded below masses of 4.4 TeV, and non-thermal quantum black holes are excluded below masses of 3.8 (6.2) TeV for Randall--Sundrum (Arkani-Hamed--Dimopoulous--Dvali) models with one (six) extra dimensions. .
211. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Constraints on non-Standard Model Higgs boson interactions in an effective Lagrangian using differential cross sections measured in the H→γγ decay channel at √s=8 TeV with the ATLAS detector , Phys. Lett. B, 10.1016/j.physletb.2015.11.071, 753, 69-85, 2016.02, The strength and tensor structure of the Higgs boson's interactions are investigated within an effective field theory framework, which allows new CP-even and CP-odd interactions that can lead to changes in the kinematic properties of the Higgs boson and associated jet spectra. The parameters of the effective field theory are probed using a fit to five differential cross sections previously measured by the ATLAS experiment in the H→γγ decay channel with an integrated luminosity of 20.3 fb−1 at √s=8 TeV. In order to perform a simultaneous fit to the five distributions, the statistical correlations between them are determined by re-analysing the H→γγ candidate events in the proton-proton collision data. No significant deviations from the Standard Model are observed and limits on the effective field theory parameters are derived. The statistical correlations are made publicly available to allow for future analysis of theories with non-Standard Model interactions. .
212. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the charge asymmetry in top-quark pair production in the lepton-plus-jets final state in pp collision data at √s=8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-016-3910-6, 76, 87, 2016.02, This paper reports inclusive and differential measurements of the tt¯ charge asymmetry AC in 20.3 fb−1 of s√=8 TeV pp collisions recorded by the ATLAS experiment at the Large Hadron Collider at CERN. Three differential measurements are performed as a function of the invariant mass, transverse momentum and longitudinal boost of the tt¯ system. The tt¯ pairs are selected in the single-lepton channels (e or μ) with at least four jets, and a likelihood fit is used to reconstruct the tt¯ event kinematics. A Bayesian unfolding procedure is performed to infer the asymmetry at parton level from the observed data distribution. The inclusive tt¯ charge asymmetry is measured to be AC=0.009±0.005 (stat.+syst.). The inclusive and differential measurements are compatible with the values predicted by the Standard Model. .
213. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for direct scalar top pair production in final states with two tau leptons in pp collisions at √s=8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-016-3897-z, 76, 81, 2016.02, A search for direct pair production of the supersymmetric partner of the top quark, decaying via a scalar tau to a nearly massless gravitino, has been performed using 20 fb−1 of proton-proton collision data at √s=8 TeV. The data were collected by the ATLAS experiment at the LHC in 2012. Top squark candidates are searched for in events with either two hadronically decaying tau leptons, one hadronically decaying tau and one light lepton, or two light leptons. No significant excess over the Standard Model expectation is found. Exclusion limits at 95% confidence level are set as a function of the top squark and scalar tau masses. Depending on the scalar tau mass, ranging from the 87 GeV LEP limit to the top squark mass, lower limits between 490 GeV and 650 GeV are placed on the top squark mass within the model considered. .
214. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of four-lepton production in pp collisions at √s= 8 TeV with the ATLAS detector , Phys. Lett. B, 10.1016/j.physletb.2015.12.048, 753, 552-572, 2016.02, The four-lepton (4ℓ, ℓ=e,μ) production cross section is measured in the mass range from 80 to 1000 GeV using 20.3 fb−1 of data in pp collisions at √s=8 TeV collected with the ATLAS detector at the LHC. The 4ℓ events are produced in the decays of resonant Z and Higgs bosons and the non-resonant ZZ continuum originating from qq¯, gg, and qg initial states. A total of 476 signal candidate events are observed with a background expectation of 26.2±3.6 events, enabling the measurement of the integrated cross section and the differential cross section as a function of the invariant mass and transverse momentum of the four-lepton system.
In the mass range above 180 GeV, assuming the theoretical constraint on the qq¯ production cross section calculated with perturbative NNLO QCD and NLO electroweak corrections, the signal strength of the gluon-fusion component relative to its leading-order prediction is determined to be μgg=2.4±1.0(stat.)±0.5(syst.)±0.8(theory). .
215. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the production of single vector-like and excited quarks in the Wt final state in pp collisions at √s=8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP02(2016)110, 2016, 02, 110, 2016.02, A search for vector-like quarks and excited quarks in events containing a top quark and a W boson in the final state is reported here. The search is based on 20.3fb−1 of proton--proton collision data taken at the LHC at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector. Events with one or two leptons, and one, two or three jets are selected with the additional requirement that at least one jet contains a b-quark. Single-lepton events are also required to contain at least one large-radius jet from the hadronic decay of a high-pT W boson or a top quark. No significant excess over the expected background is observed and upper limits on the cross-section times branching ratio for different vector-like quark and excited-quark model masses are derived. For the excited-quark production and decay to Wt with unit couplings, quarks with masses below 1500 GeV are excluded and coupling-dependent limits are set. .
216. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the differential cross-section of highly boosted top quarks as a function of their transverse momentum in √s = 8 TeV proton--proton collisions using the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.93.032009, 93, 032009, 2016.02, The differential cross-section for pair production of top quarks with high transverse momentum is measured in 20.3 fb−1 of proton-proton collisions at a center-of-mass energy of 8 TeV. The measurement is performed for tt¯ events in the lepton+jets channel. The cross-section is reported as a function of the hadronically decaying top quark transverse momentum for values above 300 GeV. The hadronically decaying top quark is reconstructed as an anti-kt jet with radius parameter R=1.0 and identified with jet substructure techniques. The observed yield is corrected for detector effects to obtain a cross-section at particle level in a fiducial region close to the event selection. A parton-level cross-section extrapolated to the full phase space is also reported for top quarks with transverse momentum above 300 GeV. The predictions of a majority of next-to-leading-order and leading-order matrix-element Monte Carlo generators are found to agree with the measured cross-sections. .
217. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A search for prompt lepton-jets in pp collisions at √s=8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP02(2016)062, 2016, 02, 062, 2016.02, A search is presented for a new, light boson with a mass of about 1 GeV and decaying promptly to jets of collimated electrons and/or muons (lepton-jets). The analysis is performed with 20.3 fb−1 of data collected by the ATLAS detector at the Large Hadron Collider in proton--proton collisions at a centre-of-mass energy of 8 TeV. Events are required to contain at least two lepton-jets. This study finds no statistically significant deviation from predictions of the Standard Model and places 95\% confidence-level upper limits on the contribution of new phenomena beyond the SM, incuding SUSY-portal and Higgs-portal models, on the number of events with lepton-jets. .
218. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of the Higgs boson production and decay rates and coupling strengths using pp collision data at √s=7 and 8 TeV in the ATLAS experiment , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3769-y, 76, 6, 2016.01, Combined analyses of the Higgs boson production and decay rates as well as its coupling strengths to vector bosons and fermions are presented. The combinations include the results of the analyses of the H→γγ,ZZ∗,WW∗,Zγ,bb¯,ττ and μμ decay modes, and the constraints on the associated production with a pair of top quarks and on the off-shell coupling strengths of the Higgs boson. The results are based on the LHC proton-proton collision datasets, with integrated luminosities of up to 4.7 fb−1 at √s=7 TeV and 20.3 fb−1 at √s=8 TeV, recorded by the ATLAS detector in 2011 and 2012. Combining all production modes and decay channels, the measured signal yield, normalised to the Standard Model expectation, is 1.18+0.15−0.14. The observed Higgs boson production and decay rates are interpreted in a leading-order coupling framework, exploring a wide range of benchmark coupling models both with and without assumptions on the Higgs boson width and on the Standard Model particle content in loop processes. The data are found to be compatible with the Standard Model expectations for a Higgs boson at a mass of 125.36 GeV for all models considered. .
219. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for an additional, heavy Higgs boson in the H→ZZ decay channel at √s = 8 TeV in pp collision data with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3820-z, 76, 45, 2016.01, Search for an additional, heavy Higgs boson in the H→ZZ decay channel at √s = 8 TeV in pp collision data with the ATLAS detector.
220. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Study of the B+c→J/ψD+s and B+c→J/ψD∗+s decays with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3743-8, 76, 4, 2016.01, The decays B+c→J/ψD+s and B+c→J/ψD∗+s are studied with the ATLAS detector at the LHC using a dataset corresponding to integrated luminosities of 4.9 fb−1 and 20.6 fb−1 of pp collisions collected at centre-of-mass energies s√=7 TeV and 8 TeV, respectively. Signal candidates are identified through J/ψ→μ+μ− and D(∗)+s→ϕπ+(γ/π0) decays. With a two-dimensional likelihood fit involving the B+c reconstructed invariant mass and an angle between the μ+ and D+s candidate momenta in the muon pair rest frame, the yields of B+c→J/ψD+s and B+c→J/ψD∗+s, and the transverse polarisation fraction in B+c→J/ψD∗+s decay are measured. The transverse polarisation fraction is determined to be Γ±±(B+c→J/ψD∗+s)/Γ(B+c→J/ψD∗+s)=0.38±0.23±0.07, and the derived ratio of the branching fractions of the two modes is BB+c→J/ψD∗+s/BB+c→J/ψD+s=2.8+1.2−0.8±0.3, where the first error is statistical and the second is systematic. Finally, a sample of B+c→J/ψπ+ decays is used to derive the ratios of branching fractions BB+c→J/ψD+s/BB+c→J/ψπ+=3.8±1.1±0.4±0.2 and BB+c→J/ψD∗+s/BB+c→J/ψπ+=10.4±3.1±1.5±0.6, where the third error corresponds to the uncertainty of the branching fraction of D+s→ϕ(K+K−)π+ decay. The available theoretical predictions are generally consistent with the measurement. .
221. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Searches for scalar leptoquarks in pp collisions at √s = 8 TeV with the ATLAS detector. , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3823-9, 76, 5, 2016.01, Searches for pair-produced scalar leptoquarks are performed using 20 fb−1 of proton-proton collision data provided by the LHC and recorded by the ATLAS detector at √s=8 TeV. Events with two electrons (muons) and two or more jets in the final state are used to search for first (second)-generation leptoquarks. The results from two previously published ATLAS analyses are interpreted in terms of third-generation leptoquarks decaying to bντb¯ντ¯ and tντt¯ντ¯ final states. No statistically significant excess above the Standard Model expectation is observed in any channel and scalar leptoquarks are excluded at 95% CL with masses up to mLQ1 < 1050 GeV for first-generation leptoquarks, mLQ2 < 1000 GeV for second-generation leptoquarks, mLQ3< 625 GeV for third-generation leptoquarks in the bντb¯ντ¯ channel, and 200
222. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for flavour-changing neutral current top-quark decays to qZ in pp collision data collected with the ATLAS detector at √s=8 TeV, Eur. Phys. J. C, 10.1140/epjc/s10052-015-3851-5, 76, 12, 2016.01, A search for the flavour-changing neutral-current decay t→qZ is presented. Data collected by the ATLAS detector during 2012 from proton-proton collisions at the Large Hadron Collider at a centre-of-mass energy of √s=8 TeV, corresponding to an integrated luminosity of 20.3 fb−1, are analysed. Top-quark pair-production events with one top quark decaying through the t→qZ (q=u,c) channel and the other through the dominant Standard Model mode t→bW are considered as signal. Only the decays of the Z boson to charged leptons and leptonic W boson decays are used. No evidence for a signal is found and an observed (expected) upper limit on the t→qZ branching ratio of 7×10−4 (8×10−4) is set at the 95% confidence level. .
223. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of fiducial cross-sections for tt¯ production with one or two additional b-jets in pp collisions at √s=8 TeV using the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3852-4, 76, 11, 2016.01, Fiducial cross-sections for tt¯ production with one or two additional b-jets are reported, using an integrated luminosity of 20.3 fb−1 of proton--proton collisions at a centre-of-mass energy of 8 TeV at the Large Hadron Collider, collected with the ATLAS detector. The cross-section times branching ratio for tt¯ events with at least one additional b-jet is measured to be 950 ± 70 (stat.) +240−190 (syst.) fb in the lepton-plus-jets channel and 50 ± 10 (stat.) +15−10 (syst.) fb in the eμ channel. The cross-section times branching ratio for events with at least two additional b-jets is measured to be 19.3 ± 3.5 (stat.) ± 5.7 (syst.) fb in the dilepton channel (eμ,\,μμ, and \,ee) using a method based on tight selection criteria, and 13.5 ± 3.3 (stat.) ± 3.6 (syst.) fb using a looser selection that allows the background normalisation to be extracted from data. The latter method also measures a value of 1.30 ± 0.33 (stat.) ± 0.28 (syst.)\% for the ratio of tt¯ production with two additional b-jets to tt¯ production with any two additional jets. All measurements are in good agreement with recent theory predictions. .
224. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for invisible decays of a Higgs boson using vector-boson fusion in pp collisions at √s=8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP01(2016)172, 2016, 01, 172, 2016.01, A search for a Higgs boson produced via vector-boson fusion and decaying into invisible particles is presented, using 20.3 fb−1 of proton--proton collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the LHC. For a Higgs boson with a mass of 125 GeV, assuming the Standard Model production cross section, an upper bound of 0.28 is set on the branching fraction of H→ invisible at 95% confidence level, where the expected upper limit is 0.31. The results are interpreted in models of Higgs-portal dark matter where the branching fraction limit is converted into upper bounds on the dark-matter--nucleon scattering cross section as a function of the dark-matter particle mass, and compared to results from the direct dark-matter detection experiments. .
225. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for single top-quark production via flavour changing neutral currents at 8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-016-3876-4, 76, 55, 2016.01, A search for single top-quark production via flavour changing neutral current processes from gluon plus up- or charm--quark initial states in proton--proton collisions at the LHC is presented. Data collected with the ATLAS detector in 2012 at a centre-of-mass energy of 8TeV and corresponding to an integrated luminosity of 20.3fb−1 are used. Candidate events for a top quark decaying into a lepton, a neutrino and a jet are selected and classified into signal- and background-like candidates using a neural network. No signal is observed and an upper limit on the production cross-section multiplied by the t→Wb branching fraction is set. The observed 95% CL limit is σqg→t×B(t→Wb)<3.4pb and the expected 95% CL limit is σqg→t×B(t→Wb)<2.9pb. The observed limit can be interpreted as upper limits on the coupling constants of the flavour changing neutral current interactions divided by the scale of new physics κugt/Λ<5.8×10−3TeV−1 and κcgt/Λ<13×10−3TeV−1 and on the branching fractions B(t→ug)<4×10−5 and B(t→cg)<20×10−5. .
226. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a high-mass Higgs boson decaying to a W boson pair in pp collisions at √s = 8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP01(2016)032, 2016, 01, 032, 2016.01, A search for a high-mass Higgs boson H is performed in the H→WW→ℓνℓν and H→WW→ℓνqq decay channels, using pp collision data corresponding to an integrated luminosity of 20.3 fb−1, collected at √s= 8 TeV by the ATLAS detector at the Large Hadron Collider. No evidence of a high-mass Higgs boson is found. Limits on σH×BR(H→WW) as a function of the Higgs boson mass mH are determined in three different scenarios: one in which the heavy Higgs boson has a narrow width compared to the experimental resolution, one a width increasing with the boson mass and modeled by the complex-pole scheme following the same behavior as in the Standard Model, and one for intermediate widths. The upper range of the search is mH=1500 GeV for the narrow-width scenario and mH=1000 GeV for the other two scenarios. The lower edge of the search range is 200−300 GeV and depends on the analysis channel and search scenario. For each scenario, individual and combined limits from the two WW decay channels are presented. At mH=1500 GeV, the highest mass point tested, σH⋅BR(H→WW) for a narrow-width Higgs boson is constrained to be less than 22 fb and 6.6 fb at the 95% CL for the gluon fusion and vector-boson fusion production modes, respectively. .
227. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the production cross-section of a single top quark in association with a W boson at 8 TeV with the ATLAS, JHEP, 10.1007/JHEP01(2016)064, 2016, 01, 064, 2016.01, The cross-section for the production of a single top quark in association with a W boson in proton--proton collisions at √s=8 TeV is measured. The dataset corresponds to an integrated luminosity of 20.3 fb−1, collected by the ATLAS detector in 2012 at the Large Hadron Collider at CERN. Events containing two leptons and one central b-jet are selected. The Wt signal is separated from the backgrounds using boosted decision trees, each of which combines a number of discriminating variables into one classifier. Production of Wt events is observed with a significance of 7.7σ. The cross-section is extracted in a profile likelihood fit to the classifier output distributions. The Wt cross-section, inclusive of decay modes, is measured to be 23.0±1.3(stat.)+3.2−3.5(syst.)±1.1(lumi.) pb. The measured cross-section is used to extract a value for the CKM matrix element |Vtb| of 1.01±0.10 and a lower limit of 0.80 at the 95\% confidence level. The cross-section for the production of a top quark and a W boson is also measured in a fiducial acceptance requiring two leptons with pT>25 GeV and |η|<2.5, one jet with pT>20 GeV and |η|<2.5, and EmissT>20 GeV, including both Wt and top-quark pair events as signal. The measured value of the fiducial cross-section is 0.85±0.01(stat.)+0.06−0.07(syst.)±0.03(lumi.) pb. .
228. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the correlations between the polar angles of leptons from top quark decays in the helicity basis at √s=7 TeV using the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.93.012002, 93, 012002, 2016.01, A measurement of the correlations between the polar angles of leptons from the decay of pair-produced t and t¯ quarks in the helicity basis is reported, using proton-proton collision data collected by the ATLAS detector at the LHC. The dataset corresponds to an integrated luminosity of 4.6fb−1 at a center-of-mass energy of s√=7TeV collected during 2011. Candidate events are selected in the dilepton topology with large missing transverse momentum and at least two jets. The angles θ1 and θ2 between the charged leptons and the direction of motion of the parent quarks in the tt¯ rest frame are sensitive to the spin information, and the distribution of {\mbox{cosθ1⋅cosθ2}} is sensitive to the spin correlation between the t and t¯ quarks. The distribution is unfolded to parton level and compared to the next-to-leading order prediction. A good agreement is observed. .
229. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the production of neighbouring jets in lead-lead collisions at √sNN=2.76 TeV with the ATLAS detector , Phys. Lett. B, 10.1016/j.physletb.2015.10.059, 751, 376-395, 2015.12, This Letter presents measurements of correlated production of nearby jets in Pb+Pb collisions at √sNN=2.76 TeV using the ATLAS detector at the Large Hadron Collider. The measurement was performed using 0.14 nb−1 of data recorded in 2011. The production of correlated jet pairs was quantified using the rate, RΔR, of "neighbouring" jets that accompany "test" jets within a given range of angular distance, ΔR, in the pseudorapidity--azimuthal angle plane. The jets were measured in the ATLAS calorimeter and were reconstructed using the anti-kt algorithm with radius parameters d=0.2, 0.3, and 0.4. RΔR was measured in different Pb+Pb collision centrality bins, characterized by the total transverse energy measured in the forward calorimeters. A centrality dependence of RΔR is observed for all three jet radii with RΔR found to be lower in central collisions than in peripheral collisions. The ratios formed by the RΔR values in different centrality bins and the values in the 40-80 % centrality bin are presented. .
230. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the branching ratio Γ(Λ0b→ψ(2S)Λ0)/Γ(Λ0b→J/ψΛ0) with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2015.10.009, 751, 63-80, 2015.12, An observation of the Λ0b→ψ(2S)Λ0 decay and a comparison of its branching fraction with that of the Λ0b→J/ψΛ0 decay has been made with the ATLAS detector in proton--proton collisions at √s=8TeV at the LHC using an integrated luminosity of 20.6fb−1. The J/ψ and ψ(2S) mesons are reconstructed in their decays to a muon pair, while the Λ0→pπ− decay is exploited for the Λ0 baryon reconstruction. The Λ0b baryons are reconstructed with transverse momentum pT>10GeV and pseudorapidity |η|<2.1. The measured branching ratio of the Λ0b→ψ(2S)Λ0 and Λ0b→J/ψΛ0 decays is Γ(Λ0b→ψ(2S)Λ0)/Γ(Λ0b→J/ψΛ0)=0.501±0.033(stat)±0.019(syst), lower than the expectation from the covariant quark model. .
231. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Determination of the ratio of b-quark fragmentation fractions fs/fd in pp collisions at √s=7 TeV with the ATLAS detector , Phys. Rev. Lett., 10.1103/PhysRevLett.115.262001, 115, 262001, 2015.12, With an integrated luminosity of 2.47 fb−1 recorded by the ATLAS experiment at the LHC, the exclusive decays B0s→J/ψϕ and B0d→J/ψK∗0 of B mesons produced in pp collisions at √s=7 TeV are used to determine the ratio of fragmentation fractions fs/fd. From the observed B0s→J/ψϕ and B0d→J/ψK∗0 yields, the quantity fsfdB(B0s→J/ψϕ)B(B0d→J/ψK∗0) is measured to be 0.199 ± 0.004(stat) ± 0.008(sys). Using a recent theory prediction for B(B0s→J/ψϕ)B(B0d→J/ψK∗0) yields fsfd= 0.240 ± 0.004(stat) ± 0.010(sys) ± 0.017(th). This result is based on a new approach that provides a significant improvement of the world average. .
232. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for pair production of a new heavy quark that decays into a W boson and a light quark in pp collisions at √s=8 TeV with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.92.112007, 92, 112007, 2015.12, A search is presented for pair production of a new heavy quark (Q) that decays into a W boson and a light quark (q) in the final state where one W boson decays leptonically (to an electron or muon plus a neutrino) and the other W boson decays hadronically. The analysis is performed using an integrated luminosity of 20.3 fb−1 of pp collisions at √s=8 TeV collected by the ATLAS detector at the LHC. No evidence of QQ¯ production is observed. New chiral quarks with masses below 690 GeV are excluded at 95% confidence level, assuming BR(Q→Wq)=1. Results are also interpreted in the context of vectorlike quark models, resulting in the limits on the mass of a vectorlike quark in the two-dimensional plane of BR(Q→Wq) versus BR(Q→Hq). .
233. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for flavour-changing neutral current top quark decays t→Hq in pp collisions at √s=8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP12(2015)061, 2015, 12, 061, 2015.12, A search for flavour-changing neutral current decays of a top quark to an up-type quark (q=u,c) and the Standard Model Higgs boson, where the Higgs boson decays to bb¯, is presented. The analysis searches for top quark pair events in which one top quark decays to Wb, with the W boson decaying leptonically, and the other top quark decays to Hq. The search is based on pp collisions at s√=8 TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider and uses an integrated luminosity of 20.3 fb−1. Data are analysed in the lepton-plus-jets final state, characterised by an isolated electron or muon and at least four jets. The search exploits the high multiplicity of b-quark jets characteristic of signal events, and employs a likelihood discriminant that uses the kinematic differences between the signal and the background, which is dominated by tt¯→WbWb decays. No significant excess of events above the background expectation is found, and observed (expected) 95% CL upper limits of 0.56% (0.42%) and 0.61% (0.64%) are derived for the t→Hc and t→Hu branching ratios respectively. The combination of this search with other ATLAS searches in the H→γγ and H→WW∗,ττ decay modes significantly improves the sensitivity, yielding observed (expected) 95% CL upper limits on the t→Hc and t→Hu branching ratios of 0.46% (0.25%) and 0.45% (0.29%) respectively. The corresponding combined observed (expected) upper limits on the |λtcH| and |λtuH| couplings are 0.13 (0.10) and 0.13 (0.10) respectively. These are the most restrictive direct bounds on tqH interactions measured so far. .
234. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of four-jet differential cross sections in √s=8 TeV proton-proton collisions using the ATLAS detector , JHEP, 10.1007/JHEP12(2015)105, 2015, 12, 105, 2015.12, Differential cross sections for the production of at least four jets have been measured in proton-proton collisions at √s=8 TeV at the Large Hadron Collider using the ATLAS detector. Events are selected if the four anti-kt R=0.4 jets with the largest transverse momentum (pT) within the rapidity range |y|<2.8 are well separated (dRmin4j>0.65), all have pT>64 GeV, and include at least one jet with pT>100 GeV. The dataset corresponds to an integrated luminosity of 20.3 fb−1. The cross sections, corrected for detector effects, are compared to leading-order and next-to-leading-order calculations as a function of the jet momenta, invariant masses, minimum and maximum opening angles and other kinematic variables. .
235. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new light gauge bosons in Higgs boson decays to four-lepton final states in pp collisions at √s=8 TeV with the ATLAS detector at the LHC , Phys. Rev. D, 10.1103/PhysRevD.92.092001, 92, 092001, 2015.11, This paper presents a search for Higgs bosons decaying to four leptons, either electrons or muons, via one or two light exotic gauge bosons Zd, H→ZZd→4ℓ or H→ZdZd→4ℓ. The search was performed using pp collision data corresponding to an integrated luminosity of about 20 fb−1 at the center-of-mass energy of √s=8TeV recorded with the ATLAS detector at the Large Hadron Collider. The observed data are well described by the Standard Model prediction. Upper bounds on the branching ratio of H→ZZd→4ℓ and on the kinetic mixing parameter between the Zd and the Standard Model hypercharge gauge boson are set in the range (1--9)×10−5 and (4--17)×10−2 respectively, at 95% confidence level assuming the Standard Model branching ratio of H→ZZ∗→4ℓ, for Zd masses between 15 and 55 GeV. Upper bounds on the effective mass mixing parameter between the Z and the Zd are also set using the branching ratio limits in the H→ZZd→4ℓ search, and are in the range (1.5--8.7)×10−4 for 15
236. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for lepton-flavour-violating H→μτ decays of the Higgs boson with the ATLAS detector , JHEP, 10.1007/JHEP11(2015)211, 2015, 11, 211, 2015.11, A direct search for lepton-flavour-violating (LFV) H→μτ decays of the recently discovered Higgs boson with the ATLAS detector at the LHC is presented. The analysis is performed in the H→μτhad channel, where τhad is a hadronically decaying τ-lepton. The search is based on the data sample of proton--proton collisions collected by the ATLAS experiment corresponding to an integrated luminosity of 20.3 fb−1 at a centre-of-mass energy of √s=8 TeV. No statistically significant excess of data over the predicted background is observed. The observed (expected) 95% confidence-level upper limit on the branching fraction, Br(H→μτ), is 1.85% (1.24%). .
237. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Constraints on new phenomena via Higgs boson couplings and invisible decays with the ATLAS detector , JHEP, 10.1007/JHEP11(2015)206, 2015, 11, 206, 2015.11, The ATLAS experiment at the LHC has measured the Higgs boson couplings and mass, and searched for invisible Higgs boson decays, using multiple production and decay channels with up to 4.7 fb−1 of pp collision data at √s=7 TeV and 20.3 fb−1 at √s=8 TeV. In the current study, the measured production and decay rates of the observed Higgs boson in the γγ, ZZ, WW, Zγ, bb, ττ, and μμ decay channels, along with results from the associated production of a Higgs boson with a top-quark pair, are used to probe the scaling of the couplings with mass. Limits are set on parameters in extensions of the Standard Model including a composite Higgs boson, an additional electroweak singlet, and two-Higgs-doublet models. Together with the measured mass of the scalar Higgs boson in the γγ and ZZ decay modes, a lower limit is set on the pseudoscalar Higgs boson mass of mA>370 GeV in the "hMSSM" simplified Minimal Supersymmetric Standard Model. Results from direct searches for heavy Higgs bosons are also interpreted in the hMSSM. Direct searches for invisible Higgs boson decays in the vector-boson fusion and associated production of a Higgs boson with W/Z (Z→ll, W/Z→jj) modes are statistically combined to set an upper limit on the Higgs boson invisible branching ratio of 0.25. The use of the measured visible decay rates in a more general coupling fit improves the upper limit to 0.23, constraining a Higgs portal model of dark matter. .
238. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Searches for Higgs boson pair production in the hh→bbττ,γγWW∗,γγbb,bbbb channels with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.92.092004, 92, 092004, 2015.11, Searches for both resonant and non-resonant Higgs boson pair production are performed in the hh→bbττ,γγWW∗ final states using 20.3 fb−1 of pp collision data at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. No evidence of their production is observed and 95\% confidence level upper limits on the production cross sections are set. These results are then combined with the published results of the hh→γγbb,bbbb analyses. An upper limit of 0.69 (0.47) pb on the non-resonant Standard Model like hh production is observed (expected), corresponding to 70 (48) times of the SM gg→hh cross section. For production via narrow resonances, cross section limits of hh production from a heavy Higgs boson decay are set as a function of the heavy Higgs boson mass. The observed (expected) limits range from 2.1 (1.1) pb at 260 GeV to 0.011 (0.018) pb at 1000 GeV. These results are interpreted in the context of two simplified scenarios of the Minimal Supersymmetric Standard Model. .
239. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the tt¯W and tt¯Z production cross sections in pp collisions at √s=8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP11(2015)172, 2015, 11, 172, 2015.11, The production cross sections of top-quark pairs in association with massive vector bosons have been measured using data from pp collisions at √s=8 TeV. The dataset corresponds to an integrated luminosity of 20.3 fb−1 collected by the ATLAS detector in 2012 at the LHC. Final states with two, three or four leptons are considered. A fit to the data considering the tt¯W and tt¯Z processes simultaneously yields a significance of 5.0σ (4.2σ) over the background-only hypothesis for tt¯W (tt¯Z) production. The measured cross sections are σtt¯W=369+100−91 fb and σtt¯Z=176+58−52 fb. The background-only hypothesis with neither tt¯W nor tt¯Z production is excluded at 7.1σ. All measurements are consistent with next-to-leading-order calculations for the tt¯W and tt¯Z processes. .
240. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Two-particle Bose--Einstein correlations in pp collisions at √s= 0.9 and 7 TeV measured with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3644-x, 75, 466, 2015.10, The paper presents studies of Bose-Einstein Correlations (BEC) for pairs of like-sign charged particles measured in the kinematic range pT> 100 MeV and |η|< 2.5 in proton--proton collisions at centre-of-mass energies of 0.9 and 7 TeV with the ATLAS detector at the CERN Large Hadron Collider. The integrated luminosities are approximately 7 μb−1, 190 μb−1 and 12.4 nb−1 for 0.9 TeV, 7 TeV minimum-bias and 7 TeV high-multiplicity data samples, respectively. The multiplicity dependence of the BEC parameters characterizing the correlation strength and the correlation source size are investigated for charged-particle multiplicities of up to 240. A saturation effect in the multiplicity dependence of the correlation source size is observed using the high-multiplicity 7 TeV data sample. The dependence of the BEC parameters on the average transverse momentum of the particle pair is also investigated. .
241. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Analysis of events with b-jets and a pair of leptons of the same charge in pp collisions at √s=8 TeV with the ATLAS detector, JHEP, 10.1007/JHEP10(2015)150, 2015, 10, 150, 2015.10, An analysis is presented of events containing jets including at least one b-tagged jet, sizeable missing transverse momentum, and at least two leptons including a pair of the same electric charge, with the scalar sum of the jet and lepton transverse momenta being large. A data sample with an integrated luminosity of 20.3 fb−1 of pp collisions at √s=8 TeV recorded by the ATLAS detector at the Large Hadron Collider is used. Standard Model processes rarely produce these final states, but there are several models of physics beyond the Standard Model that predict an enhanced rate of production of such events; the ones considered here are production of vector-like quarks, enhanced four-top-quark production, pair production of chiral b′-quarks, and production of two positively charged top quarks. Eleven signal regions are defined; subsets of these regions are combined when searching for each class of models. In the three signal regions primarily sensitive to positively charged top quark pair production, the data yield is consistent with the background expectation. There are more data events than expected from background in the set of eight signal regions defined for searching for vector-like quarks and chiral b′-quarks, but the significance of the discrepancy is less than two standard deviations. The discrepancy reaches 2.5 standard deviations in the set of five signal regions defined for searching for four-top-quark production. The results are used to set 95% CL limits on various models. .
242. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for massive, long-lived particles using multitrack displaced vertices or displaced lepton pairs in pp collisions at √s = 8 TeV with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.92.072004, 92, 072004, 2015.10, Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. This article presents the results of a search for events containing at least one long-lived particle that decays at a significant distance from its production point into two leptons or into five or more charged particles. This analysis uses a data sample of proton-proton collisions at √s = 8 TeV corresponding to an integrated luminosity of 20.3 fb−1 collected in 2012 by the ATLAS detector operating at the Large Hadron Collider. No events are observed in any of the signal regions, and limits are set on model parameters within supersymmetric scenarios involving R-parity violation, split supersymmetry, and gauge mediation. In some of the search channels, the trigger and search strategy are based only on the decay products of individual long-lived particles, irrespective of the rest of the event. In these cases, the provided limits can easily be reinterpreted in different scenarios. .
243. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the top quark branching ratios into channels with leptons and quarks with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.92.072005, 92, 072005, 2015.10, Measurements of the branching ratios of top quark decays into leptons and jets using events with tt¯ (top antitop) pairs are reported. Events were recorded with the ATLAS detector at the LHC in pp collisions at a center-of-mass energy of 7 TeV. The collected data sample corresponds to an integrated luminosity of 4.6 fb−1. The measured top quark branching ratios agree with the Standard Model predictions within the measurement uncertainties of a few percent. .
244. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Study of the spin and parity of the Higgs boson in diboson decays with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3685-1, 75, 476, 2015.10, Studies of the spin, parity and tensor couplings of the Higgs boson in the H→ZZ∗→4ℓ, H→WW∗→eνμν and H→γγ decay processes at the LHC are presented. The investigations are based on 25 fb−1 of pp collision data collected by the ATLAS experiment at √s=7 TeV and √s=8 TeV. The Standard Model (SM) Higgs boson hypothesis, corresponding to the quantum numbers JP=0+, is tested against several alternative spin scenarios, including non-SM spin-0 and spin-2 models with universal and non-universal couplings to fermions and vector bosons. All tested alternative models are excluded in favour of the SM Higgs boson hypothesis at more than 99.9% confidence level. Using the H→ZZ∗→4ℓ and H→WW∗→eνμν decays, the tensor structure of the HVV interaction in the spin-0 hypothesis is also investigated. The observed distributions of variables sensitive to the non-SM tensor couplings are compatible with the SM predictions and constraints on the non-SM couplings are derived. .
245. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), ATLAS Run 1 searches for direct pair production of third-generation squarks at the Large Hadron Collider , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3726-9, 75, 510, 2015.10, This paper reviews and extends searches for the direct pair production of the scalar supersymmetric partners of the top and bottom quarks in proton-proton collisions collected by the ATLAS collaboration during the LHC Run 1. Most of the analyses use 20 fb−1 of collisions at a centre-of-mass energy of √s = 8 TeV, although in some case an additional 4.7 fb−1 of collision data at √s = 7 TeV are used. New analyses are introduced to improve the sensitivity to specific regions of the model parameter space. Since no evidence of third-generation squarks is found, exclusion limits are derived by combining several analyses and are presented in both a simplified model framework, assuming simple decay chains, as well as within the context of more elaborate phenomenological supersymmetric models. .
246. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Determination of the top-quark pole mass using $t t$ +1-jet events collected with the ATLAS experiment in 7 TeV pp collisions , JHEP, 10.1007/JHEP10(2015)121, 2015, 10, 121, 2015.10, The normalized differential cross section for top-quark pair production in association with at least one jet is studied as a function of the inverse of the invariant mass of the tt¯+1-jet system. This distribution can be used for a precise determination of the top-quark mass since gluon radiation depends on the mass of the quarks. The experimental analysis is based on proton-proton collision data collected by the ATLAS detector at the LHC with a centre-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.6 fb−1. The selected events were identified using the lepton+jets top-quark-pair decay channel, where lepton refers to either an electron or a muon. The observed distribution is compared to a theoretical prediction at next-to-leading-order accuracy in quantum chromodynamics using the pole-mass scheme. With this method, the measured value of the top-quark pole mass, mpolet, is: mpolet =173.7 ± 1.5 (stat.) ± 1.4 (syst.) +1.0−0.5 (theory) GeV. This result represents the most precise measurement of the top-quark pole mass to date. .
247. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Summary of the searches for squarks and gluinos using √s = 8 TeV pp collisions with the ATLAS experiment at the LHC , JHEP, 10.1007/JHEP10(2015)054, 2015, 10, 054, 2015.10, A summary is presented of ATLAS searches for gluinos and first- and second-generation squarks in final states containing jets and missing transverse momentum, with or without leptons or b-jets, in the √s = 8 TeV data set collected at the Large Hadron Collider in 2012. This paper reports the results of new interpretations and statistical combinations of previously published analyses, as well as a new analysis. Since no significant excess of events over the Standard Model expectation is observed, the data are used to set limits in a variety of models. In all the considered simplified models that assume R-parity conservation, the limit on the gluino mass exceeds 1150 GeV at 95% confidence level, for an LSP mass smaller than 100 GeV. Furthermore, exclusion limits are set for left-handed squarks in a phenomenological MSSM model, a minimal Supergravity/Constrained MSSM model, R-parity-violation scenarios, a minimal gauge-mediated supersymmetry breaking model, a natural gauge mediation model, a non-universal Higgs mass model with gaugino mediation and a minimal model of universal extra dimensions. .
248. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for photonic signatures of gauge-mediated supersymmetry in 8 TeV pp collisions with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.92.072001, 92, 072001, 2015.10, A search is presented for photonic signatures motivated by generalised models of gauge-mediated supersymmetry breaking. This search makes use of 20.3fb−1 of proton-proton collision data at √s=8 TeV recorded by the ATLAS detector at the LHC, and explores models dominated by both strong and electroweak production of supersymmetric partner states. Four experimental signatures incorporating an isolated photon and significant missing transverse momentum are explored. These signatures include events with an additional photon, lepton, b-quark jet, or jet activity not associated with any specific underlying quark flavor. No significant excess of events is observed above the Standard Model prediction and model-dependent 95% confidence-level exclusion limits are set. .
249. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Z boson production in p+Pb collisions at √sNN=5.02 TeV measured with the ATLAS detector , Phys. Rev. C, 10.1103/PhysRevC.92.044915, 92, 044915, 2015.10, The ATLAS Collaboration has measured the inclusive production of Z bosons via their decays into electron and muon pairs in p+Pb collisions at √sNN=5.02 TeV at the Large Hadron Collider. The measurements are made using data corresponding to integrated luminosities of 29.4 nb−1 and 28.1 nb−1 for Z→ee and Z→μμ, respectively. The results from the two channels are consistent and combined to obtain a cross section times the Z→ℓℓ branching ratio, integrated over the rapidity region |y∗Z|<3.5, of 139.8 ± 4.8 (stat.) ± 6.2 (syst.) ± 3.8 (lumi.) nb. Differential cross sections are presented as functions of the Z boson rapidity and transverse momentum, and compared with models based on parton distributions both with and without nuclear corrections. The centrality dependence of Z boson production in p+Pb collisions is measured and analyzed within the framework of a standard Glauber model and the model's extension for fluctuations of the underlying nucleon-nucleon scattering cross section. .
250. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Summary of the ATLAS experiment's sensitivity to supersymmetry after LHC Run 1 - interpreted in the phenomenological MSSM, JHEP, 10.1007/JHEP10(2015)134, 2015, 10, 134, 2015.10, A summary of the constraints from the ATLAS experiment on R-parity conserving supersymmetry is presented. Results from 22 separate ATLAS searches are considered, each based on analysis of up to 20.3 fb−1 of proton-proton collision data at the centre-of-mass energy of √s = 7 and 8 TeV at the Large Hadron Collider. The results are interpreted in the context of the 19-parameter phenomenological minimal supersymmetric standard model, in which the lightest supersymmetric particle is a neutralino, taking into account constraints from previous precision electroweak and flavour measurements as well as from dark matter related measurements. The results are presented in terms of constraints on supersymmetric particle masses and are compared to limits from simplified models. The impact of ATLAS searches on parameters such as the dark matter relic density, the couplings of the observed Higgs boson, and the degree of electroweak fine-tuning is also shown. Spectra for surviving supersymmetry model points with low fine-tunings are presented. .
251. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the forward-backward asymmetry of electron and muon pair-production in pp collisions at √s = 7 TeV with the ATLAS detector , JHEP, 10.1007/JHEP09(2015)049, 2015, 09, 049, 2015.09, This paper presents measurements from the ATLAS experiment of the forward-backward asymmetry in the reaction pp→Z/γ∗→l+l−, with l being electrons or muons, and the extraction of the effective weak mixing angle. The results are based on the full set of data collected in 2011 in pp collisions at the LHC at √s = 7 TeV, corresponding to an integrated luminosity of 4.8 fb−1. The measured asymmetry values are found to be in agreement with the corresponding Standard Model predictions. The combination of the muon and electron channels yields a value of the effective weak mixing angle of 0.2308±0.0005(stat.)±0.0006(syst.)±0.0009(PDF), where the first uncertainty corresponds to data statistics,the second to systematic effects and the third to knowledge of the parton density functions. This result agrees with the current world average from the Particle Data Group fit. .
252. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the correlation between flow harmonics of different order in lead-lead collisions at √sNN=2.76 TeV with the ATLAS detector , Phys. Rev. C, 10.1103/PhysRevC.92.034903, 92, 034903, 2015.09, Correlations between the elliptic or triangular flow coefficients vm (m=2 or 3) and other flow harmonics vn (n=2 to 5) are measured using √sNN=2.76 TeV Pb+Pb collision data collected in 2010 by the ATLAS experiment at the LHC, corresponding to an integrated lumonisity of 7 μb−1. The vm-vn correlations are measured in midrapidity as a function of centrality, and, for events within the same centrality interval, as a function of event ellipticity or triangularity defined in a forward rapidity region. For events within the same centrality interval, v3 is found to be anticorrelated with v2 and this anticorrelation is consistent with similar anticorrelations between the corresponding eccentricities ϵ2 and ϵ3. On the other hand, it is observed that v4 increases strongly with v2, and v5 increases strongly with both v2 and v3. The trend and strength of the vm-vn correlations for n=4 and 5 are found to disagree with ϵm-ϵn correlations predicted by initial-geometry models. Instead, these correlations are found to be consistent with the combined effects of a linear contribution to vn and a nonlinear term that is a function of v22 or of v2v3, as predicted by hydrodynamic models. A simple two-component fit is used to separate these two contributions. The extracted linear and nonlinear contributions to v4 and v5 are found to be consistent with previously measured event-plane correlations. .
253. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of charged-particle spectra in Pb+Pb collisions at √sNN=2.76 TeV with the ATLAS detector at the LHC , JHEP, 10.1007/JHEP09(2015)050, 2015, 09, 050, 2015.09, Charged-particle spectra obtained in 0.15 nb−1 of Pb+Pb interactions at √sNN=2.76TeV and 4.2 pb−1 of pp interactions at √s=2.76 TeV with the ATLAS detector at the LHC are presented in a wide transverse momentum (0.5
254. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Higgs bosons decaying to aa in the μμττ final state in pp collisions at √s= 8 TeV with the ATLAS experiment , Phys. Rev. D, 10.1103/PhysRevD.92.052002, 92, 052002, 2015.09, A search for the decay to a pair of new particles of either the 125 GeV Higgs boson (h) or a second CP-even Higgs boson (H) is presented. The dataset correspods to an integrated luminosity of 20.3 fb−1 of pp collisions at √s= 8 TeV recorded by the ATLAS experiment at the LHC in 2012. The search was done in the context of the next-to-minimal supersymmetric standard model, in which the new particles are the lightest neutral pseudoscalar Higgs bosons (a). One of the two a bosons is required to decay to two muons while the other is required to decay to two τ-leptons. No significant excess is observed above the expected backgrounds in the dimuon invariant mass range from 3.7 GeV to 50 GeV. Upper limits are placed on the production of h→aa relative to the Standard Model gg→h production, assuming no coupling of the a boson to quarks. The most stringent limit is placed at 3.5\% for ma= 3.75 GeV. Upper limits are also placed on the production cross section of H→aa from 2.33 pb to 0.72 pb, for fixed ma = 5 GeV with mH ranging from 100 GeV to 500 GeV. .
255. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of differential J/ψ production cross-sections and forward-backward ratio in p+Pb collisions with the ATLAS detector , Phys. Rev. C, 10.1103/PhysRevC.92.034904, 92, 034904, 2015.09, Measurements of differential cross-sections for J/ψ production in p+Pb collisions at √sNN = 5.02 TeV at the LHC with the ATLAS detector are presented. The data set used corresponds to an integrated luminosity of 28.1 nb−1. The J/ψ mesons are reconstructed in the dimuon decay channel over the transverse momentum range 8
256. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Higgs boson pair production in the bb¯bb¯ final state from pp collisions at √s=8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3628-x, 75, 412, 2015.09, A search for Higgs boson pair production pp→hh is performed with 19.5 fb−1 of proton--proton collision data at √s= 8 TeV, which were recorded by the ATLAS detector at the Large Hadron Collider in 2012. The decay products of each Higgs boson are reconstructed as a high-momentum bb¯ system with either a pair of small-radius jets or a single large-radius jet, the latter exploiting jet substructure techniques and associated b-tagged track-jets. No evidence for resonant or non-resonant Higgs boson pair production is observed. The data are interpreted in the context of the Randall--Sundrum model with a warped extra dimension as well as the two-Higgs-doublet model. An upper limit on the cross-section for pp→G∗KK→hh→bb¯bb¯ of 3.2 (2.3) fb is set for a Kaluza--Klein graviton G∗KK mass of 1.0 (1.5) TeV, at the 95\% confidence level. The search for non-resonant Standard Model hh production sets an observed 95\% confidence level upper limit on the production cross-section σ(pp→hh→bb¯bb¯) of 202 fb, compared to a SM prediction of σ(pp→hh→bb¯bb¯)=3.6±0.5 fb. .
257. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for high-mass diboson resonances with boson-tagged jets in proton-proton collisions at √s=8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP12(2015)055, 2015, 12, 055, 2015.09, A search is performed for narrow resonances decaying into WW, WZ, or ZZ boson pairs using 20.3 fb−1 of proton-proton collision data at a centre-of-mass energy of √s = 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. Diboson resonances with masses in the range from 1.3 to 3.0 TeV are sought after using the invariant mass distribution of dijets where both jets are tagged as a boson jet, compatible with a highly boosted W or Z boson decaying to quarks, using jet mass and substructure properties. The largest deviation from a smoothly falling background in the observed dijet invariant mass distribution occurs around 2 TeV in the WZ channel, with a global significance of 2.5 standard deviations. Exclusion limits at the 95% confidence level are set on the production cross section times branching ratio for the WZ final state of a new heavy gauge boson, W′, and for the WW and ZZ final states of Kaluza--Klein excitations of the graviton in a bulk Randall--Sundrum model, as a function of the resonance mass. W′ bosons with couplings predicted by the extended gauge model in the mass range from 1.3 to 1.5 TeV are excluded at 95% confidence level. .
258. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Dark Matter in Events with Missing Transverse Momentum and a Higgs Boson Decaying to Two Photons in pp Collisions at √s=8 TeV with the ATLAS Detector , Phys. Rev. Lett., 10.1103/PhysRevLett.115.131801, 115, 131801, 2015.09, Results of a search for new phenomena in events with large missing transverse momentum and a Higgs boson decaying to two photons are reported. Data from proton-proton collisions at a center-of-mass energy of 8 TeV and corresponding to an integrated luminosity of 20.3 fb−1 have been collected with the ATLAS detector at the LHC. The observed data are well described by the expected Standard Model backgrounds. Upper limits on the cross section of events with large missing transverse momentum and a Higgs boson candidate are also placed. Exclusion limits are presented for models of physics beyond the Standard Model featuring dark-matter candidates. .
259. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for heavy lepton resonances decaying to a Z boson and a lepton in pp collisions at √s=8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP09(2015)108, 2015, 09, 108, 2015.09, A search for heavy leptons decaying to a Z boson and an electron or a muon is presented. The search is based on pp collision data taken at √s=8 TeV by the ATLAS experiment at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb−1. Three high-transverse-momentum electrons or muons are selected, with two of them required to be consistent with originating from a Z boson decay. No significant excess above Standard Model background predictions is observed, and 95% confidence level limits on the production cross section of high-mass trilepton resonances are derived. The results are interpreted in the context of vector-like lepton and type-III seesaw models. For the vector-like lepton model, most heavy lepton mass values in the range 114-176 GeV are excluded. For the type-III seesaw model, most mass values in the range 100-468 GeV are excluded. .
260. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for metastable heavy charged particles with large ionisation energy loss in pp collisions at sqrt(s) = 8 TeV using the ATLAS experiment , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3609-0, 75, 407, 2015.09, Many extensions of the Standard Model predict the existence of charged heavy long-lived particles, such as R-hadrons or charginos. These particles, if produced at the Large Hadron Collider, should be moving non-relativistically and are therefore identifiable through the measurement of an anomalously large specific energy loss in the ATLAS pixel detector. Measuring heavy long-lived particles through their track parameters in the vicinity of the interaction vertex provides sensitivity to metastable particles with lifetimes from 0.6 ns to 30 ns. A search for such particles with the ATLAS detector at the Large Hadron Collider is presented, based on a data sample corresponding to an integrated luminosity of 18.4 fb−1 of pp collisions at √s = 8 TeV. No significant deviation from the Standard Model background expectation is observed, and lifetime-dependent upper limits on R-hadrons and chargino production are set. Gluino R-hadrons with 10 ns lifetime and masses up to 1185 GeV are excluded at 95% confidence level, and so are charginos with 15 ns lifetime and masses up to 482 GeV. .
261. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Modelling Z→ττ processes in ATLAS with τ-embedded Z→μμ data , JINST, 10.1088/1748-0221/2015/9/P09018, 10, P09018, 2015.09, This paper describes the concept, technical realisation and validation of a largely data-driven method to model events with Z→ττ decays. In Z→μμ events selected from proton--proton collision data recorded at √s=8 TeV with the ATLAS experiment at the LHC in 2012, the Z decay muons are replaced by τ leptons from simulated Z→ττ decays at the level of reconstructed tracks and calorimeter cells. The τ lepton kinematics are derived from the kinematics of the original muons. Thus, only the well-understood decays of the Z boson and τ leptons as well as the detector response to the τ decay products are obtained from simulation. All other aspects of the event, such as the Z boson and jet kinematics as well as effects from multiple interactions, are given by the actual data. This so-called τ-embedding method is particularly relevant for Higgs boson searches and analyses in ττ final states, where Z→ττ decays constitute a large irreducible background that cannot be obtained directly from data control samples. In this paper, the relevant concepts are discussed based on the implementation used in the ATLAS Standard Model H→ττ analysis of the full datataset recorded during 2011 and 2012. .
262. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of colour flow with the jet pull angle in tt¯ events using the ATLAS detector at √s=8 TeV, Phys. Lett. B, 10.1016/j.physletb.2015.09.051, 750, 475-493, 2015.09, The distribution and orientation of energy inside jets is predicted to be an experimental handle on colour connections between the hard--scatter quarks and gluons initiating the jets. This Letter presents a measurement of the distribution of one such variable, the jet pull angle. The pull angle is measured for jets produced in tt¯ events with one W boson decaying leptonically and the other decaying to jets using 20.3 fb−1 of data recorded with the ATLAS detector at a centre-of-mass energy of √s=8 TeV at the LHC. The jet pull angle distribution is corrected for detector resolution and acceptance effects and is compared to various models. .
263. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of transverse energy--energy correlations in multi-jet events in pp collisions at √s=7 TeV using the ATLAS detector and determination of the strong coupling constant αs(mZ), Phys. Lett. B, 10.1016/j.physletb.2015.09.050, 750, 427-447, 2015.09, High transverse momentum jets produced in pp collisions at a centre of mass energy of 7 TeV are used to measure the transverse energy-energy correlation function and its associated azimuthal asymmetry. The data were recorded with the ATLAS detector at the LHC in the year 2011 and correspond to an integrated luminosity of 158 pb−1. The selection criteria demand the average transverse momentum of the two leading jets in an event to be larger than 250 GeV. The data at detector level are well described by Monte Carlo event generators. They are unfolded to the particle level and compared with theoretical calculations at next-to-leading-order accuracy. The agreement between data and theory is good and provides a precision test of perturbative Quantum Chromodynamics at large momentum transfers. From this comparison, the strong coupling constant given at the Z boson mass is determined to be αs(mZ)=0.1173±0.0010 (exp.) +0.0065−0.0026 (theo.). .
264. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for heavy long-lived multi-charged particles in pp collisions at √s=8 TeV using the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3534-2, 75, 362, 2015.08, A search for heavy long-lived multi-charged particles is performed using the ATLAS detector at the LHC. Data collected in 2012 at √s=8 TeV from pp collisions corresponding to an integrated luminosity of 20.3 fb−1 are examined. Particles producing anomalously high ionisation, consistent with long-lived massive particles with electric charges from |q|=2e to |q|=6e are searched for. No signal candidate events are observed, and 95\% confidence level cross-section upper limits are interpreted as lower mass limits for a Drell--Yan production model. The mass limits range between 660 and 785 GeV. .
265. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of the Total and Differential Higgs Boson Production Cross Sections Combining the H→γγ and H→ZZ∗→4ℓ Decay Channels at √s=8 TeV with the ATLAS Detector , Phys. Rev. Lett., 10.1103/PhysRevLett.115.091801, 115, 091801, 2015.08, Measurements of the total and differential cross sections of Higgs boson production are performed using 20.3 fb−1 of pp collisions produced by the Large Hadron Collider at a center-of-mass energy of √s=8 TeV and recorded by the ATLAS detector. Cross sections are obtained from measured H→γγ and H→ZZ∗→4ℓ event yields, which are combined accounting for detector efficiencies, fiducial acceptances and branching fractions. Differential cross sections are reported as a function of Higgs boson transverse momentum, Higgs boson rapidity, number of jets in the event, and transverse momentum of the leading jet. The total production cross section is determined to be σpp→H=33.0±5.3(stat)±1.6(sys)pb. The measurements are compared to state-of-the-art predictions. .
266. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for high-mass diphoton resonances in pp collisions at √s=8 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.92.032004, 92, 032004, 2015.08, This article describes a search for high-mass resonances decaying to a pair of photons using a sample of 20.3 fb−1 of pp collisions at √s=8 TeV recorded with the ATLAS detector at the Large Hadron Collider. The data are found to be in agreement with the Standard Model prediction, and limits are reported in the framework of the Randall-Sundrum model. This theory leads to the prediction of graviton states, the lightest of which could be observed at the Large Hadron Collider. A lower limit of 2.66 (1.41) TeV at 95% confidence level is set on the mass of the lightest graviton for couplings of k/MPl=0.1 (0.01). .
267. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for production of vector-like quark pairs and of four top quarks in the lepton-plus-jets final state in pp collisions at √s=8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP08(2015)105, 2015, 08, 105, 2015.08, A search for pair production of vector-like quarks, both up-type (T) and down-type (B), as well as for four-top-quark production, is presented. The search is based on pp collisions at √s=8 TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 20.3 fb−1. Data are analysed in the lepton-plus-jets final state, characterised by an isolated electron or muon with high transverse momentum, large missing transverse momentum and multiple jets. Dedicated analyses are performed targeting three cases: a T quark with significant branching ratio to a W boson and a b-quark (TT¯→Wb+X), and both a T quark and a B quark with significant branching ratio to a Higgs boson and a third-generation quark (TT¯→Ht+X and BB¯→Hb+X respectively). No significant excess of events above the Standard Model expectation is observed, and 95% CL lower limits are derived on the masses of the vector-like T and B quarks under several branching ratio hypotheses assuming contributions from T→Wb, Zt, Ht and B→Wt, Zb, Hb decays. The 95% CL observed lower limits on the T quark mass range between 715 GeV and 950 GeV for all possible values of the branching ratios into the three decay modes, and are the most stringent constraints to date. Additionally, the most restrictive upper bounds on four-top-quark production are set in a number of new physics scenarios. .
268. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A search for tt¯ resonances using lepton-plus-jets events in proton--proton collisions at √s=8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP08(2015)148, 2015, 08, 148, 2015.08, A search for new particles that decay into top quark pairs is reported. The search is performed with the ATLAS experiment at the LHC using an integrated luminosity of 20.3 fb−1 of proton-proton collision data collected at a centre-of-mass energy of √s=8 TeV. The lepton-plus-jets final state is used, where the top pair decays to W+bW−b¯, with one W boson decaying leptonically and the other hadronically. The invariant mass spectrum of top quark pairs is examined for local excesses or deficits that are inconsistent with the Standard Model predictions. No evidence for a top quark pair resonance is found, and 95% confidence-level limits on the production rate are determined for massive states in benchmark models. The upper limits on the cross-section times branching ratio of a narrow Z′ boson decaying to top pairs range from 4.2 pb to 0.03 pb for resonance masses from 0.4 TeV to 3.0 TeV. A narrow leptophobic topcolour Z′ boson with mass below 1.8 TeV is excluded. Upper limits are set on the cross-section times branching ratio for a broad colour-octet resonance with Γ/m= 15% decaying to tt¯. These range from 2.5 pb to 0.03 pb for masses from 0.4 TeV to 3.0 TeV. A Kaluza-Klein excitation of the gluon in a Randall-Sundrum model is excluded for masses below 2.2 TeV. .
269. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Observation and measurement of Higgs boson decays to WW* with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.92.012006, 92, 012006 , 2015.08, We report the observation of Higgs boson decays to WW∗ based on an excess over background of 6.1 standard deviations in the dilepton final state, where the Standard Model expectation is 5.8 standard deviations. Evidence for the vector-boson fusion (VBF) production process is obtained with a significance of 3.2 standard deviations. The results are obtained from a data sample corresponding to an integrated luminosity of 25fb−1 from √s=7 and 8 TeV pp collisions recorded by the ATLAS detector at the LHC. For a Higgs boson mass of 125.36 GeV, the ratio of the measured value to the expected value of the total production cross section times branching fraction is 1.09+0.16−0.15(stat)+0.17−0.14(syst). The corresponding ratios for the gluon fusion and vector-boson fusion production mechanisms are 1.02±0.19(stat)+0.22−0.18(syst) and 1.27+0.44−0.40(stat)+0.30−0.21(syst), respectively. At s√=8 TeV, the total production cross sections are measured to be σ(gg→ H→WW∗)=4.6±0.9(stat)+0.8−0.7(syst)pb and σ(VBF H→WW∗)=0.51+0.17−0.15(stat)+0.13−0.08(syst)pb. The fiducial cross section is determined for the gluon-fusion process in exclusive final states with zero or one associated jet. .
270. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena in events with three or more charged leptons in pp collisions at √s=8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP08(2015)138, 2015, 08, 138, 2015.08, A generic search for anomalous production of events with at least three charged leptons is presented. The data sample consists of pp collisions at √s=8 TeV collected in 2012 by the ATLAS experiment at the CERN Large Hadron Collider, and corresponds to an integrated luminosity of 20.3 fb−1. Events are required to have at least three selected lepton candidates, at least two of which must be electrons or muons, while the third may be a hadronically decaying tau. Selected events are categorized based on their lepton flavour content and signal regions are constructed using several kinematic variables of interest. No significant deviations from Standard Model predictions are observed. Model-independent upper limits on contributions from beyond the Standard Model phenomena are provided for each signal region, along with prescription to re-interpret the limits for any model. Constraints are also placed on models predicting doubly charged Higgs bosons and excited leptons. For doubly charged Higgs bosons decaying to eτ or μτ, lower limits on the mass are set at 400 GeV at 95% confidence level. For excited leptons, constraints are provided as functions of both the mass of the excited state and the compositeness scale Λ, with the strongest mass constraints arising in regions where the mass equals Λ. In such scenarios, lower mass limits are set at 3.0 TeV for excited electrons and muons, 2.5 TeV for excited taus, and 1.6 TeV for every excited-neutrino flavour. .
271. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for type-III Seesaw heavy leptons in pp collisions at √s=8 TeV with the ATLAS Detector , Phys. Rev. D, 10.1103/PhysRevD.92.032001, 92, 032001, 2015.08, A search for the pair-production of heavy leptons (N0,L±) predicted by the type-III seesaw theory formulated to explain the origin of small neutrino masses is presented. The decay channels N0→W±l∓ (ℓ=e,μ,τ) and L±→W±ν (ν=νe,νμ,ντ) are considered. The analysis is performed using the final state that contains two leptons (electrons or muons), two jets from a hadronically decaying W boson, and large missing transverse momentum. The data used in the measurement correspond to an integrated luminosity of 20.3fb−1 of pp collisions at √s=8 TeV collected by the ATLAS detector at the LHC. No evidence of heavy lepton pair-production is observed. Heavy leptons with masses below 325--540 GeV are excluded at the 95% confidence level, depending on the theoretical scenario considered. .
272. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the associated production of the Higgs boson with a top quark pair in multilepton final states with the ATLAS detector , Phys. Lett. B, 10.1016/j.physletb.2015.07.079, 749, 519-541, 2015.08, A search for the associated production of the Higgs boson with a top quark pair is performed in multilepton final states using 20.3 fb−1 of proton-proton collision data recorded by the ATLAS experiment at √s=8 TeV at the Large Hadron Collider. Five final states, targeting the decays H→WW∗, ττ, and ZZ∗, are examined for the presence of the Standard Model (SM) Higgs boson: two same-charge light leptons (e or μ) without a hadronically decaying τ lepton; three light leptons; two same-charge light leptons with a hadronically decaying τ lepton; four light leptons; and one light lepton and two hadronically decaying τ leptons. No significant excess of events is observed above the background expectation. The best fit for the tt¯H production cross section, assuming a Higgs boson mass of 125 GeV, is 2.1+1.4−1.2 times the SM expectation, and the observed (expected) upper limit at the 95% confidence level is 4.7 (2.4) times the SM rate. The p-value for compatibility with the background-only hypothesis is 1.8σ; the expectation in the presence of a Standard Model signal is 0.9σ. .
273. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Study of (W/Z)H production and Higgs boson couplings using H→WW∗ decays with the ATLAS detector , JHEP, 10.1007/JHEP08(2015)137, 2015, 08, 137, 2015.08, A search for Higgs boson production in association with a W or Z boson, in the H→WW∗ decay channel, is performed with a data sample collected with the ATLAS detector at the LHC in proton-proton collisions at centre-of-mass energies s√=7 TeV and 8 TeV, corresponding to integrated luminosities of 4.5 fb−1 and 20.3 fb−1, respectively. The WH production mode is studied in two-lepton and three-lepton final states, while two-lepton and four-lepton final states are used to search for the ZH production mode. The observed significance, for the combined WH and ZH production, is 2.5 standard deviations while a significance of 0.9 standard deviations is expected in the Standard Model Higgs boson hypothesis. The ratio of the combined WH and ZH signal yield to the Standard Model expectation, μVH, is found to be μVH=3.0+1.3−1.1(stat.)+1.0−0.7(sys.) for the Higgs boson mass of 125.36 GeV. The WH and ZH production modes are also combined with the gluon fusion and vector boson fusion production modes studied in the H→WW∗→ℓνℓν decay channel, resulting in an overall observed significance of 6.5 standard deviations and μggF+VBF+VH=1.16+0.16−0.15(stat.)+0.18−0.15(sys.). The results are interpreted in terms of scaling factors of the Higgs boson couplings to vector bosons (κV) and fermions (κF); the combined results are: |κV|=1.06+0.10−0.10, |κF|=0.85+0.26−0.20. .
274. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √s=8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3517-3, 75, 299, 2015.07, Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √s=8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT>120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between EmissT>150 GeV and EmissT>700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with large extra spatial dimensions, pair production of weakly interacting dark matter candidates, and production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presented. .
275. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A search for high-mass resonances decaying to τ+τ− in pp collisions at √s=8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP07(2015)157, 2015, 07, 157, 2015.07, A search for high-mass resonances decaying into τ+τ− final states using proton-proton collisions at √s=8 TeV produced by the Large Hadron Collider is presented. The data were recorded with the ATLAS detector and correspond to an integrated luminosity of 19.5-20.3 fb−1. No statistically significant excess above the Standard Model expectation is observed; 95% credibility upper limits are set on the cross section times branching fraction of Z′ resonances decaying into τ+τ− pairs as a function of the resonance mass. As a result, Z′ bosons of the Sequential Standard Model with masses less than 2.02 TeV are excluded at 95% credibility. The impact of the fermionic couplings on the Z′ acceptance is investigated and limits are also placed on a Z′ model that exhibits enhanced couplings to third-generation fermions. .
276. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Constraints on the off-shell Higgs boson signal strength in the high-mass ZZ and WW final states with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3542-2, 75, 335, 2015.07, Measurements of the ZZ and WW final states in the mass range above the 2mZ and 2mW thresholds provide a unique opportunity to measure the off-shell coupling strength of the Higgs boson. This paper presents constraints on the off-shell Higgs boson event yields normalised to the Standard Model prediction (signal strength) in the ZZ→4ℓ, ZZ→2ℓ2ν and WW→eνμν final states. The result is based on pp collision data collected by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 20.3 fb-1 at a collision energy of √s=8 TeV. Using the CLs method, the observed 95% confidence level (CL) upper limit on the off-shell signal strength is in the range 5.1-8.6, with an expected range of 6.7-11.0. In each case the range is determined by varying the unknown gg→ZZ and gg→WW background K-factor from higher-order QCD corrections between half and twice the value of the known signal K-factor. Assuming the relevant Higgs boson couplings are independent of the energy scale of the Higgs production, a combination with the on-shell measurements yields an observed (expected) 95\% CL upper limit on ΓH/ΓSMH in the range 4.5- -7.5 (6.5- -11.2) using the same variations of the background K-factor. Assuming that the unknown gg→VV background K-factor is equal to the signal K-factor,this translates into an observed (expected) 95% CL upper limit on the Higgs boson total width of 22.7 (33.0) MeV. .
277. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Evidence of Wγγ production in pp collisions at √s=8 TeV and limits on anomalous quartic gauge couplings with the ATLAS detector , Phys. Rev. Lett., 10.1103/PhysRevLett.115.031802, 115, 031802, 2015.07, This Letter reports evidence of triple gauge boson production pp→W(ℓν)γγ+X, which is accessible for the first time with the 8 TeV LHC data set. The fiducial cross section for this process is measured in a data sample corresponding to an integrated luminosity of 20.3 fb−1, collected by the ATLAS detector in 2012. Events are selected using the W boson decay to eν or μν as well as requiring two isolated photons. The measured cross section is used to set limits on anomalous quartic gauge couplings in the high diphoton mass region. .
278. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for supersymmetry in events containing a same-flavour opposite-sign dilepton pair, jets, and large missing transverse momentum in √s=8 TeV pp collisions with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3518-2, 75, 318, 2015.07, Two searches for supersymmetric particles in final states containing a same-flavour opposite-sign lepton pair, jets and large missing transverse momentum are presented. The proton-proton collision data used in these searches were collected at a centre-of-mass energy √s=8 TeV by the ATLAS detector at the Large Hadron Collider and corresponds to an integrated luminosity of 20.3 fb−1. Two leptonic production mechanisms are considered: decays of squarks and gluinos with Z bosons in the final state, resulting in a peak in the dilepton invariant mass distribution around the Z-boson mass; and decays of neutralinos (e.g. χ~02→ℓ+ℓ−χ~01), resulting in a kinematic endpoint in the dilepton invariant mass distribution. For the former, an excess of events above the expected Standard Model background is observed, with a significance of 3 standard deviations. In the latter case, the data are well-described by the expected Standard Model background. The results from each channel are interpreted in the context of several supersymmetric models involving the production of squarks and gluinos. .
279. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a Heavy Neutral Particle Decaying to eμ, eτ, or μτ in pp Collisions at √s=8 TeV with the ATLAS Detector , Phys. Rev. Lett., 10.1103/PhysRevLett.115.031801, 115, 031801, 2015.07, This Letter presents a search for a heavy neutral particle decaying into an opposite-sign different-flavor dilepton pair, e±μ∓, e±τ∓, or μ±τ∓ using 20.3 fb−1 of pp collision data at √s=8 TeV collected by the ATLAS detector at the LHC. The numbers of observed candidate events are compatible with the Standard Model expectations. Limits are set on the cross section of new phenomena in two scenarios: the production of ν~τ in R-parity-violating supersymmetric models and the production of a lepton-flavor-violating Z′ vector boson. .
280. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Standard Model Higgs boson produced in association with top quarks and decaying into bb¯ in pp collisions at √s=8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3543-1, 75, 349, 2015.07, A search for the Standard Model Higgs boson produced in association with a pair of top quarks, tt¯H, is presented. The analysis uses 20.3 fb−1 of pp collision data at √s = 8 TeV, collected with the ATLAS detector at the Large Hadron Collider during 2012. The search is designed for the H to bb¯ decay mode and uses events containing one or two electrons or muons. In order to improve the sensitivity of the search, events are categorised according to their jet and b-tagged jet multiplicities. A neural network is used to discriminate between signal and background events, the latter being dominated by tt¯+jets production. In the single-lepton channel, variables calculated using a matrix element method are included as inputs to the neural network to improve discrimination of the irreducible tt¯+bb¯ background. No significant excess of events above the background expectation is found and an observed (expected) limit of 3.4 (2.2) times the Standard Model cross section is obtained at 95% confidence level. The ratio of the measured tt¯H signal cross section to the Standard Model expectation is found to be μ = 1.5 ± 1.1 assuming a Higgs boson mass of 125 GeV. .
281. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the top quark mass in the tt¯→lepton+jets and tt¯→dilepton channels using √s=7 TeV ATLAS data , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3544-0, 75, 330, 2015.07, The top quark mass was measured in the channels tt¯→lepton+jets and tt¯→dilepton (lepton=e,μ) based on ATLAS data recorded in 2011. The data were taken at the LHC with a proton--proton centre-of-mass energy of √s=7 TeV and correspond to an integrated luminosity of 4.6fb−1. The tt¯→lepton+jets analysis uses a three-dimensional template technique which determines the top quark mass together with a global jet energy scale factor (JSF), and a relative b-to-light-jet energy scale factor (bJSF), where the terms b-jets and light-jets refer to jets originating from b-quarks and u,d,c,s-quarks or gluons, respectively. The analysis of the tt¯→dilepton channel exploits a one-dimensional template method using the mℓb observable, defined as the average invariant mass of the two lepton+b-jet pairs in each event. The top quark mass is measured to be 172.33±0.75(stat)±1.02(syst) GeV, and 173.79±0.54(stat)±1.30(syst) GeV in the tt¯→lepton+jets and tt¯→dilepton channels, respectively. The combination of the two results yields mtop=172.99±0.48(stat)±0.78(syst) GeV, with a total uncertainty of 0.91 GeV. .
282. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a new resonance decaying to a W or Z boson and a Higgs boson in the ℓℓ/ℓν/νν+bb¯ final states with the ATLAS Detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3474-x, 75, 263, 2015.07, A search for a new resonance decaying to a W or Z boson and a Higgs boson in the ℓℓ/ℓν/νν+bb¯ final states is performed using 20.3 fb−1 of pp collision data recorded at √s= 8 TeV with the ATLAS detector at the Large Hadron Collider. The search is conducted by examining the WH/ZH invariant mass distribution for a localized excess. No significant deviation from the Standard Model background prediction is observed. The results are interpreted in terms of constraints on the Minimal Walking Technicolor model and on a simplified approach based on a phenomenological Lagrangian of Heavy Vector Triplets. .
283. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for low-scale gravity signatures in multi-jet final states with the ATLAS detector at √s=8 TeV, JHEP, 10.1007/JHEP07(2015)032, 2015, 07, 032, 2015.07, We search for evidence of physics beyond the Standard Model in the production of final states with multiple high transverse momentum jets, using 20.3 fb−1 of proton-proton collision data recorded by the ATLAS detector at √s=8 TeV. No excess of events beyond Standard Model expectations is observed, and upper limits on the visible cross-section for non-Standard Model production of multi-jet final states are set. Using a wide variety of models for black hole and string ball production and decay, the limit on the cross-section times acceptance is as low as 0.16 fb at the 95% CL for a minimum scalar sum of jet transverse momentum in the event of about 4.3 TeV. Using models for black hole and string ball production and decay, exclusion contours are determined as a function of the production mass threshold and the gravity scale. These limits can be interpreted in terms of lower-mass limits on black hole and string ball production that range from 4.6 to 6.2 TeV..
284. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for long-lived, weakly interacting particles that decay to displaced hadronic jets in proton-proton collisions at √s=8 TeV with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.92.012010, 92, 012010, 2015.07, A search for the decay of neutral, weakly interacting, long-lived particles using data collected by the ATLAS detector at the LHC is presented. This analysis uses the full dataset recorded in 2012: 20.3 fb−1 of proton--proton collision data at √s=8 TeV. The search employs techniques for reconstructing decay vertices of long-lived particles decaying to jets in the inner tracking detector and muon spectrometer. Signal events require at least two reconstructed vertices. No significant excess of events over the expected background is found, and limits as a function of proper lifetime are reported for the decay of the Higgs boson and other scalar bosons to long-lived particles and for Hidden Valley Z′ and Stealth SUSY benchmark models. The first search results for displaced decays in Z′ and Stealth SUSY models are presented. The upper bounds of the excluded proper lifetimes are the most stringent to date. .
285. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for invisible decays of the Higgs boson produced in association with a hadronically decaying vector boson in pp collisions at √s=8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3551-1, 75, 337, 2015.07, A search for Higgs boson decays to invisible particles is performed using 20.3 fb−1 of pp collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the Large Hadron Collider. The process considered is Higgs boson production in association with a vector boson (V = W or Z) that decays hadronically, resulting in events with two or more jets and large missing transverse momentum. No excess of candidates is observed in the data over the background expectation. The results are used to constrain VH production followed by H decaying to invisible particles for the Higgs mass range 115
286. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Identification and energy calibration of hadronically decaying tau leptons with the ATLAS experiment in pp collisions at √s=8 TeV, Eur. Phys. J. C, 10.1140/epjc/s10052-015-3500-z, 75, 303, 2015.07, This paper describes the trigger and offline reconstruction, identification and energy calibration algorithms for hadronic decays of tau leptons employed for the data collected from pp collisions in 2012 with the ATLAS detector at the LHC center-of-mass energy √s=8 TeV. The performance of these algorithms is measured in most cases with Z decays to tau leptons using the full 2012 dataset, corresponding to an integrated luminosity of 20.3 fb−1. An uncertainty on the offline reconstructed tau energy scale of 2−4%, depending on transverse energy and pseudorapidity, is achieved using two independent methods. The offline tau identification efficiency is measured with a precision of 2.5% for hadronically decaying tau leptons with one associated track, and of 4% for the case of three associated tracks, inclusive in pseudorapidity and for a visible transverse energy greater than 20 GeV. For hadronic tau lepton decays selected by offline algorithms, the tau trigger identification efficiency is measured with a precision of 2−8%, depending on the transverse energy. The performance of the tau algorithms, both offline and at the trigger level, is found to be stable with respect to the number of concurrent proton-proton interactions and has supported a variety of physics results using hadronically decaying tau leptons at ATLAS. .
287. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Centrality and rapidity dependence of inclusive jet production in √sNN=5.02 TeV proton-lead collisions with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2015.07.023, 748, 392-413, 2015.07, Measurements of the centrality and rapidity dependence of inclusive jet production in √sNN=5.02 TeV proton--lead (p+Pb) collisions and the jet cross-section in s√=2.76 TeV proton--proton collisions are presented. These quantities are measured in datasets corresponding to an integrated luminosity of 27.8 nb−1 and 4.0 pb−1, respectively, recorded with the ATLAS detector at the Large Hadron Collider in 2013. The p+Pb collision centrality was characterised using the total transverse energy measured in the pseudorapidity interval −4.9<η<−3.2 in the direction of the lead beam. Results are presented for the double-differential per-collision yields as a function of jet rapidity and transverse momentum (pT) for minimum-bias and centrality-selected p+Pb collisions, and are compared to the jet rate from the geometric expectation. The total jet yield in minimum-bias events is slightly enhanced above the expectation in a pT-dependent manner but is consistent with the expectation within uncertainties. The ratios of jet spectra from different centrality selections show a strong modification of jet production at all pT at forward rapidities and for large pT at mid-rapidity, which manifests as a suppression of the jet yield in central events and an enhancement in peripheral events. These effects imply that the factorisation between hard and soft processes is violated at an unexpected level in proton-nucleus collisions. Furthermore, the modifications at forward rapidities are found to be a function of the total jet energy only, implying that the violations may have a simple dependence on the hard parton-parton kinematics. .
288. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for heavy Majorana neutrinos with the ATLAS detector in pp collisions at √s=8 TeV, JHEP, 10.1007/JHEP07(2015)162, 2015, 07, 162, 2015.07, A search for heavy Majorana neutrinos in events containing a pair of high-pT leptons of the same charge and high-pT jets is presented. The search uses 20.3fb−1 of pp collision data collected with the ATLAS detector at the CERN Large Hadron Collider with a centre-of-mass energy of √s=8 TeV. The data are found to be consistent with the background-only hypothesis based on the Standard Model expectation. In the context of a Type-I seesaw mechanism, limits are set on the production cross-section times branching ratio for production of heavy Majorana neutrinos in the mass range between 100 and 500 GeV. The limits are subsequently interpreted as limits on the mixing between the heavy Majorana neutrinos and the Standard Model neutrinos. In the context of a left-right symmetric model, limits on the production cross-section times branching ratio are set with respect to the masses of heavy Majorana neutrinos and heavy gauge bosons WR and Z′. .
289. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of exclusive γγ→ℓ+ℓ− production in proton--proton collisions at √s=7 TeV with the ATLAS detector , Phys. Lett. B, 10.1016/j.physletb.2015.07.069, 749, 242-261, 2015.07, This Letter reports a measurement of the exclusive γγ→ℓ+ℓ−(ℓ=e,μ) cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV by the ATLAS experiment at the LHC, based on an integrated luminosity of 4.6 fb−1. For the electron or muon pairs satisfying exclusive selection criteria, a fit to the dilepton acoplanarity distribution is used to extract the fiducial cross-sections. The cross-section in the electron channel is determined to be σexcl.γγ→e+e−=0.428±0.035(stat.)±0.018(syst.) pb for a phase-space region with invariant mass of the electron pairs greater than 24 GeV, in which both electrons have transverse momentum pT>12 GeV and pseudorapidity |η|<2.4. For muon pairs with invariant mass greater than 20 GeV, muon transverse momentum pT>10 GeV and pseudorapidity |η|<2.4, the cross-section is determined to be σexcl.γγ→μ+μ−=0.628±0.032(stat.)±0.021(syst.) pb. When proton absorptive effects due to the finite size of the proton are taken into account in the theory calculation, the measured cross-sections are found to be consistent with the theory prediction. .
290. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for massive supersymmetric particles decaying to many jets using the ATLAS detector in pp collisions at √s=8 TeV, Phys. Rev. D, 10.1103/PhysRevD.91.112016, 91, 112016, 2015.06, Results of a search for decays of massive particles to fully hadronic final states are presented. This search uses 20.3 fb−1 of data collected by the ATLAS detector in √s=8 TeV proton--proton collisions at the LHC. Signatures based on high jet multiplicities without requirements on the missing transverse momentum are used to search for R-parity-violating supersymmetric gluino pair production with subsequent decays to quarks. The analysis is performed using a requirement on the number of jets, in combination with separate requirements on the number of b-tagged jets, as well as a topological observable formed from the scalar sum of the mass values of large-radius jets in the event. Results are interpreted in the context of all possible branching ratios of direct gluino decays to various quark flavors. No significant deviation is observed from the expected Standard Model backgrounds estimated using jet-counting as well as data-driven templates of the total-jet-mass spectra. Gluino pair decays to ten or more quarks via intermediate neutralinos are excluded for a gluino with mass mg~<1 TeV for a neutralino mass mχ~01=500 GeV. Direct gluino decays to six quarks are excluded for mg~<917 GeV for light-flavor final states, and results for various flavor hypotheses are presented. .
291. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Differential top--antitop cross-section measurements as a function of observables constructed from final-state particles using pp collisions at √s=7 TeV in the ATLAS detector , JHEP, 10.1007/JHEP06(2015)100, 2015, 06, 100, 2015.06, Various differential cross-sections are measured in top-quark pair (tt¯) events produced in proton-proton collisions at a centre-of-mass energy of √s=7 TeV at the LHC with the ATLAS detector. These differential cross-sections are presented in a data set corresponding to an integrated luminosity of 4.6 fb−1. The differential cross-sections are presented in terms of kinematic variables, such as momentum, rapidity and invariant mass, of a top-quark proxyreferred to as the pseudo-top-quark as well as the pseudo-top-quark pair system. The dependence of the measurement on theoretical models is minimal.
The measurements are performed on tt¯ events in the lepton+jets channel, requiring exactly one charged lepton and at least four jets with at least two of them tagged as originating from a b-quark. The hadronic and leptonic pseudo-top-quarks are defined via the leptonic or hadronic decay mode of the W boson produced by the top-quark decay in events with a single charged lepton. Differential cross-section measurements of the pseudo-top-quark variables are compared with several Monte Carlo models that implement next-to-leading order or leading-order multi-leg matrix-element calculations. .
292. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a Charged Higgs Boson Produced in the Vector-boson Fusion Mode with Decay H±→W±Z using pp Collisions at √s=8 TeV with the ATLAS Experiment, Phys. Rev. Lett., 10.1103/PhysRevLett.114.231801, 114, 231801, 2015.06, A search for a charged Higgs boson, H±, decaying to a W± boson and a Z boson is presented. The search is based on 20.3 fb−1 of proton-proton collision data at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the LHC. The H± boson is assumed to be produced via vector-boson fusion and the decays W±→qq′¯ and Z→e+e−/μ+μ− are considered. The search is performed in a range of charged Higgs boson masses from 200 to 1000 GeV. No evidence for the production of an H± boson is observed. Upper limits of 31-1020 fb at 95% CL are placed on the cross section for vector-boson fusion production of an H± boson times its branching fraction to W±Z. The limits are compared with predictions from the Georgi-Machacek Higgs Triplet Model. .
293. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for vector-like B quarks in events with one isolated lepton, missing transverse momentum and jets at √s= 8TeV with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.91.112011, 91, 112011, 2015.06, A search has been performed for pair production of heavy vector-like down-type (B) quarks. The analysis explores the lepton-plus-jets final state, characterized by events with one isolated charged lepton (electron or muon), significant missing transverse momentum and multiple jets. One or more jets are required to be tagged as arising from b-quarks, and at least one pair of jets must be tagged as arising from the hadronic decay of an electroweak boson. The analysis uses the full data sample of pp collisions recorded in 2012 by the ATLAS detector at the LHC, operating at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb−1. No significant excess of events is observed above the expected background. Limits are set on vector-like B production, as a function of the B branching ratios, assuming the allowable decay modes are B→Wt/Zb/Hb. In the chiral limit with a branching ratio of 100% for the decay B→Wt, the observed (expected) 95% CL lower limit on the vector-like B mass is 810 GeV (760 GeV). In the case where the vector-like B quark has branching ratio values corresponding to those of an SU(2) singlet state, the observed (expected) 95% CL lower limit on the vector-like B mass is 640 GeV (505 GeV). The same analysis, when used to investigate pair production of a colored, charge 5/3 exotic fermion T5/3, with subsequent decay T5/3→Wt, sets an observed (expected) 95% CL lower limit on the T5/3 mass of 840 GeV (780 GeV). .
294. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for New Phenomena in Dijet Angular Distributions in Proton-Proton Collisions at √s=8 TeV Measured with the ATLAS Detector , Phys. Rev. Lett., 10.1103/PhysRevLett.114.221802, 114, 221802, 2015.06, A search for new phenomena in LHC proton-proton collisions at a center-of-mass energy of √s=8 TeV was performed with the ATLAS detector using an integrated luminosity of 17.3 fb−1. The angular distributions are studied in events with at least two jets; the highest dijet mass observed is 5.5 TeV. All angular distributions are consistent with the predictions of the Standard Model. In a benchmark model of quark contact interactions, a compositeness scale below 8.1 TeV in a destructive interference scenario and 12.0 TeV in a constructive interference scenario is excluded at 95 % CL; median expected limits are 8.9 TeV for the destructive interference scenario and 14.1 TeV for the constructive interference scenario. .
295. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the top pair production cross-section in 8 TeV proton--proton collisions using kinematic information in the lepton+jets final state with ATLAS , Phys. Rev. D, 10.1103/PhysRevD.91.112013, 91, 112013, 2015.06, A measurement is presented of the tt¯ inclusive production cross-section in pp collisions at a center-of-mass energy of √s=8 TeV using data collected by the ATLAS detector at the CERN Large Hadron Collider. The measurement was performed in the lepton+jets final state using a data set corresponding to an integrated luminosity of 20.3 fb−1. The cross-section was obtained using a likelihood discriminant fit and b-jet identification was used to improve the signal-to-background ratio. The inclusive tt¯ production cross-section was measured to be 260±1(stat.)+22−23(syst.)±8(lumi.)±4(beam) pb assuming a top-quark mass of 172.5 GeV, in good agreement with the theoretical prediction of 253+13−15 pb. The tt¯→(e,μ)+jets production cross-section in the fiducial region determined by the detector acceptance is also reported. .
296. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Determination of spin and parity of the Higgs boson in the WW∗→eνμν decay channel with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-015-3436-3, 75, 231, 2015.05, Studies of the spin and parity quantum numbers of the Higgs boson in the WW∗→eνμν final state are presented, based on proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb−1 at a centre-of-mass energy of √s=8 TeV. The Standard Model spin-parity JCP=0++ hypothesis is compared with alternative hypotheses for both spin and CP. The case where the observed resonance is a mixture of the Standard-Model-like Higgs boson and CP-even (JCP=0++) or CP-odd (JCP=0+−) Higgs boson in scenarios beyond the Standard Model is also studied. The data are found to be consistent with the Standard Model prediction and limits are placed on alternative spin and CP hypotheses, including CP mixing in different scenarios. .
297. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Observation and measurements of the production of prompt and non-prompt J/ψ mesons in association with a Z boson in proton-proton collisions at √s = 8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3406-9, 75, 229, 2015.05, The production of a Z boson in association with a J/ψ meson in proton-proton collisions probes the production mechanisms of quarkonium and heavy flavour in association with vector bosons, and allows studies of multiple parton scattering. Using 20.3fb−1 of data collected with the ATLAS experiment at the LHC in pp collisions at √s=8TeV, the first measurement of associated Z+J/ψ production is presented for both prompt and non-prompt J/ψ production, with both signatures having a significance in excess of 5σ. The inclusive production cross-sections for Z boson production (analysed in μ+μ− or e+e− decay modes) in association with prompt and non-prompt J/ψ(→μ+μ−) are measured relative to the inclusive production rate of Z bosons in the same fiducial volume to be (36.8±6.7±2.5)×10−7 and (65.8±9.2±4.2)×10−7 respectively. Normalised differential production cross-section ratios are also determined as a function of the J/ψ transverse momentum. The fraction of signal events arising from single and double parton scattering is estimated, and a lower limit of 5.3 (3.7)mb at 68 (95)% confidence level is placed on the effective cross-section regulating double parton interactions. .
298. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of three-jet production cross-sections in pp collisions at 7 TeV centre-of-mass energy using the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3363-3, 75, 228, 2015.05, Double-differential three-jet production cross-sections are measured in proton-proton collisions at a centre-of-mass energy of √s=7 TeV using the ATLAS detector at the Large Hadron Collider. The measurements are presented as a function of the three-jet mass (mjjj), in bins of the sum of the absolute rapidity separations between the three leading jets (|Y∗|). Invariant masses extending up to 5 TeV are reached for 8<|Y∗|<10. These measurements use a sample of data recorded using the ATLAS detector in 2011, which corresponds to an integrated luminosity of 4.51 fb−1. Jets are identified using the anti-kt algorithm with two different jet radius parameters, R=0.4 and R=0.6. The dominant uncertainty in these measurements comes from the jet energy scale. Next-to-leading-order QCD calculations corrected to account for non-perturbative effects are compared to the measurements. Good agreement is found between the data and the theoretical predictions based on most of the available sets of parton distribution functions, over the full kinematic range, covering almost seven orders of magnitude in the measured cross-section values. .
299. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a CP-odd Higgs boson decaying to Zh in pp collisions at √s=8 TeV with the ATLAS detector , Phys. Lett. B, 10.1016/j.physletb.2015.03.054, 744, 163-183, 2015.05, A search for a heavy, CP-odd Higgs boson, A, decaying into a Z boson and a 125 GeV Higgs boson, h, with the ATLAS detector at the LHC is presented. The search uses proton--proton collision data at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb−1. Decays of CP-even h bosons to ττ or bb pairs with the Z boson decaying to electron or muon pairs are considered, as well as h→bb decays with the Z boson decaying to neutrinos. No evidence for the production of an A boson in these channels is found and the 95% confidence level upper limits derived for σ(gg→A)×BR(A→Zh)×BR(h→ff¯) are 0.098--0.013 pb for f=τ and 0.57--0.014 pb for f=b in a range of mA= 220--1000 GeV. The results are combined and interpreted in the context of two-Higgs doublet models. .
300. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the ttbar and lepton charge asymmetry in dilepton events in √s=7 TeV data with the ATLAS detector , JHEP, 10.1007/JHEP05(2015)061, 2015, 05, 061, 2015.05, A measurement of the top-antitop (tt¯) charge asymmetry is presented using data corresponding to an integrated luminosity of 4.6 fb−1 of LHC pp collisions at a centre-of-mass energy of 7 TeV collected by the ATLAS detector. Events with two charged leptons, at least two jets and large missing transverse momentum are selected. Two observables are studied: AℓℓC based on the identified charged leptons, and Att¯C, based on the reconstructed tt¯ final state. The asymmetries are measured to be AℓℓC=0.024±0.015 (stat.)±0.009 (syst.), Att¯C=0.021±0.025 (stat.)±0.017 (syst.). The measured values are in agreement with the Standard Model predictions. .
301. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for direct production of charginos and neutralinos decaying via the 125 GeV Higgs boson in √s=8 TeV pp collisions with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3408-7, 75, 208, 2015.05, A search is presented for the direct pair production of a chargino and a neutralino pp→χ~±1χ~02, where the chargino decays to the lightest neutralino and the W boson, χ~±1→χ~01(W±→ℓ±ν), while the neutralino decays to the lightest neutralino and the 125 GeV Higgs boson, χ~02→χ~01(h→bb/γγ/ℓ±νqq). The final states considered for the search have large missing transverse momentum, an isolated electron or muon, and one of the following: either two jets identified as originating from bottom quarks, or two photons, or a second electron or muon with the same electric charge. The analysis is based on 20.3 fb−1 of √s=8 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with the Standard Model expectations, and limits are set in the context of a simplified supersymmetric model. .
302. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for production of WW/WZ resonances decaying to a lepton, neutrino and jets in pp collisions at √s = 8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3425-6, 75, 209, 2015.05, A search is presented for a narrow diboson resonances decaying to WW or WZ in the final state where one W boson decays leptonically (to an electron or a muon plus a neutrino) and the other W/Z boson decays hadronically. The analysis is performed using an integrated luminosity of 20.3 fb−1 of pp collisions at √s = 8 TeV collected by the ATLAS detector at the LHC. No evidence for resonant diboson production is observed, and resonance masses below 700 GeV and 1490 GeV are excluded at 95% confidence level for the spin-2 Randall-Sundrum bulk graviton G∗ with coupling constant of 1.0 and the extended gauge model W′ boson respectively. .
303. Georges Aad, Kiyotomo Kawagoe et al. (ATLAS Collaboration) (CMS Collaboration), Combined Measurement of the Higgs Boson Mass in pp Collisions at √s=7 and 8 TeV with the ATLAS and CMS Experiments, Phys. Rev. Lett., 10.1103/PhysRevLett.114.191803, 114, 191803, 2015.05, A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H→γγ and H→ZZ→4ℓ decay channels. The results are obtained from a simultaneous fit to the reconstructed invariant mass peaks in the two channels and for the two experiments. The measured masses from the individual channels and the two experiments are found to be consistent among themselves. The combined measured mass of the Higgs boson is mH=125.09±0.21(stat.)±0.11(syst.) GeV. .
304. B. Bilki, K. Kawagoe et al. (The CALICE collaboration), Pion and Proton showers in the CALICE scintillator-sreel analogue hadron calorimeter, JINST, 10.1088/1748-0221/10/04/P04014, 10, 04, P040014, 2015.04.
305. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Scalar Charm Quark Pair Production in pp Collisions at √s=8 TeV with the ATLAS Detector , Phys. Rev. Lett., 10.1103/PhysRevLett.114.161801, 114, 161801, 2015.04, The results of a dedicated search for pair production of scalar partners of charm quarks are reported. The search is based on an integrated luminosity of 20.3 fb−1 of pp collisions at √s=8 TeV recorded with the ATLAS detector at the LHC. The search is performed using events with large missing transverse momentum and at least two jets, where the two leading jets are each tagged as originating from c-quarks. Events containing isolated electrons or muons are vetoed. In an R-parity-conserving minimal supersymmetric scenario in which a single scalar-charm state is kinematically accessible, and where it decays exclusively into a charm quark and a neutralino, 95% confidence-level upper limits are obtained in the scalar-charm-neutralino mass plane such that, for neutralino masses below 200 GeV, scalar-charm masses up to 490 GeV are excluded. .
306. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of spin correlation in top-antitop quark events and search for stop quark pair production in proton-proton collisions at √s = 8 TeV using the ATLAS detector , Phys. Rev. Lett., 10.1103/PhysRevLett.114.142001, 114, 142001 , 2015.04, A measurement of spin correlation in tt¯ production is presented using data collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb−1. The correlation between the top and antitop quark spins is extracted from dilepton tt¯ events by using the difference in azimuthal angle between the two charged leptons in the laboratory frame. In the helicity basis the measured degree of correlation corresponds to Ahelicity=0.38±0.04, in agreement with the Standard Model prediction. A search is performed for pair production of top squarks with masses close to the top quark mass decaying to predominantly right-handed top quarks and a light neutralino, the lightest supersymmetric particle. Top squarks with masses between the top quark mass and 191 GeV are excluded at the 95% confidence level. .
307. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the top-quark mass in the fully hadronic decay channel from ATLAS data at sqrt(s) = 7 TeV, Eur. Phys. J. C, 10.1140/epjc/s10052-015-3373-1, 75, 158, 2015.04, The mass of the top quark is measured in a data set corresponding to 4.6 fb−1 of proton-proton collisions with centre-of-mass energy s√=7 TeV collected by the ATLAS detector at the LHC. Events consistent with hadronic decays of top-antitop quark pairs with at least six jets in the final state are selected. The substantial background from multijetproduction is modelled with data-driven methods that utilise the number of identified b-quark jets and the transverse momentum of the sixth leading jet,which have minimal correlation. The top-quark mass is obtained from template fits to the ratio of three-jet to dijet mass. The three-jet mass is calculated from the three jets produced in a top-quark decay. Using these three jets the dijet mass is obtained from the two jets produced in the W boson decay. The top-quark mass obtained from this fit is thus less sensitive to the uncertainty in the energy measurement of the jets. A binned likelihood fit yields a top-quark mass of mt=175.1±1.4 (stat) ±1.2 (syst) GeV. .
308. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for W' →tb →qq'bb decays in pp collisions at √s=8 TeV with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-015-3372-2, 75, 165, 2015.04, A search for a massive W′ gauge boson decaying to a top quark and a bottom quark is performed with the ATLAS detector in pp collisions at the LHC. The dataset was taken at a centre-of-mass energy of √s=8 TeV and corresponds to 20.3 fb−1 of integrated luminosity. This analysis is done in the hadronic decay mode of the top quark, where novel jet substructure techniques are used to identify jets from high-momentum top quarks. This allows for a search for high-mass W′ bosons in the range 1.5−3.0 TeV. b-tagging is used to identify jets originating from b-quarks. The data are consistent with Standard Model background-only expectations, and upper limits at 95% confidence level are set on the W′→tb cross section times branching ratio ranging from 0.16 pb to 0.33 pb for left-handed W′ bosons, and ranging from 0.10 pb to 0.21 pb for W′ bosons with purely right-handed couplings. Upper limits at 95% confidence level are set on the W′-boson coupling to tb as a function of the W′ mass using an effective field theory approach, which is independent of details of particular models predicting a W′ boson. .
309. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Observation of top-quark pair production in association with a photon and measurement of the ttbarγ production cross section in pp collisions at √s=7 TeV using the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.91.072007, 91, 072007, 2015.04, A search is performed for top-quark pairs (tt¯) produced together with a photon (γ) with transverse momentum >20 GeV using a sample of tt¯ candidate events in final states with jets, missing transverse momentum, and one isolated electron or muon. The dataset used corresponds to an integrated luminosity of 4.59 fb−1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. In total 140 and 222 tt¯γ candidate events are observed in the electron and muon channels, to be compared to the expectation of 79±26 and 120±39 non-tt¯γ background events respectively. The production of tt¯γ events is observed with a significance of 5.3 standard deviations away from the null hypothesis. The tt¯γ production cross section times the branching ratio (BR) of the single-lepton decay channel is measured in a fiducial kinematic region within the ATLAS acceptance. The measured value is σfidtt¯γ=63±8(stat.)+17−13(syst.)±1(lumi.) fb per lepton flavor, in good agreement with the leading-order theoretical calculation normalized to the next-to-leading-order theoretical prediction of 48±10 fb. .
310. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Evidence for the Higgs-boson Yukawa coupling to tau leptons with the ATLAS detector, JHEP, 10.1007/JHEP04(2015)117, 2015, 04, 117, 2015.04, Results of a search for H→ττ decays are presented, based on the full set of proton-proton collision data recorded by the ATLAS experiment at the LHC during 2011 and 2012. The data correspond to integrated luminosities of 4.5 fb−1 and 20.3 fb−1 at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV respectively. All combinations of leptonic (τ→ℓνν¯ with ℓ=e,μ) and hadronic (τ→hadronsν) tau decays are considered. An excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.5 (3.4) standard deviations. This excess provides evidence for the direct coupling of the recently discovered Higgs boson to fermions. The measured signal strength, normalised to the Standard Model expectation, of μ=1.43+0.43−0.37 is consistent with the predicted Yukawa coupling strength in the Standard Model. .
311. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at √s=8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP04(2015)116, 2015, 04, 116, 2015.04, The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider (LHC) are reported. The search is based on proton-proton collision data at a centre-of-mass energy √s=8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb−1. No significant excess above the Standard Model expectation is observed. Limits are set on the parameters of a minimal universal extra dimensions model, excluding a compactification radius of 1/Rc=950 GeV for a cut-off scale times radius (ΛRc) of approximately 30, as well as on sparticle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. .
312. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for W′→tb¯ in the lepton plus jets final state in proton-proton collisions at a centre-of-mass energy of √s = 8 TeV with the ATLAS detector , Phys. Lett. B, 10.1016/j.physletb.2015.02.051, 743, 235-255, 2015.04, A search for new charged massive gauge bosons, called W′, is performed with the ATLAS detector at the LHC, in proton-proton collisions at a centre-of-mass energy of √s = 8 TeV, using a dataset corresponding to an integrated luminosity of 20.3 fb−1. This analysis searches for W′ bosons in the W′→tb¯ decay channel in final states with electrons or muons, using a multivariate method based on boosted decision trees. The search covers masses between 0.5 and 3.0 TeV, for right-handed or left-handed W′ bosons. No significant deviation from the Standard Model expectation is observed and limits are set on the W′→tb¯ cross-section times branching ratio and on the W′-boson effective couplings as a function of the W′-boson mass using the CLs procedure. For a left-handed (right-handed) W′ boson, masses below 1.70 (1.92) TeV are excluded at 95% confidence level. .
313. M.S. Amjad, K. Kawagoe et al., Beam test performance of the SKIROC2 ASIC, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 10.1016/j.nima.2014.12.011, 778, 78-84, 2015.04.
314. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Higgs and Z Boson Decays to J/ψ gamma and Υ(nS) gamma with the ATLAS Detector, Phys. Rev. Lett., 10.1103/PhysRevLett.114.121801, 114, 121801, 2015.03, A search for the decays of the Higgs and Z bosons to J/ψγ and Υ(nS)γ (n=1,2,3) is performed with pp collision data samples corresponding to integrated luminosities of up to 20.3fb−1 collected at √s=8TeV with the ATLAS detector at the CERN Large Hadron Collider. No significant excess of events is observed above expected backgrounds and 95\% CL upper limits are placed on the branching fractions. In the J/ψγ final state the limits are 1.5×10−3 and 2.6×10−6 for the Higgs and Z boson decays, respectively, while in the Υ(1S,2S,3S)γ final states the limits are (1.3,1.9,1.3)×10−3 and (3.4,6.5,5.4)×10−6, respectively. .
315. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for charged Higgs bosons decaying via H+- -→ tau +- nu in fully hadronic final states using pp collision data at √s = 8 TeV with the ATLAS detector, JHEP, 10.1007/JHEP03(2015)088, 2015, 03, 088, 2015.03, The results of a search for charged Higgs bosons decaying to a τ lepton and a neutrino, H±→τ±ν, are presented. The analysis is based on 19.5 fb−1 of proton-proton collision data at √s=8 TeV collected by the ATLAS experiment at the Large Hadron Collider. Charged Higgs bosons are searched for in events consistent with top-quark pair production or in associated production with a top quark. The final state is characterised by the presence of a hadronic τ decay, missing transverse momentum, b-tagged jets, a hadronically decaying W boson, and the absence of any isolated electrons or muons with high transverse momenta. The data are consistent with the expected background from Standard Model processes. A statistical analysis leads to 95\% confidence-level upper limits on the product of branching ratios B(t→bH±)×B(H±→τ±ν), between 0.23% and 1.3% for charged Higgs boson masses in the range 80-160 GeV. It also leads to 95% confidence-level upper limits on the production cross section times branching ratio, σ(pp→tH±+X)×B(H±→τ±ν), between 0.76 pb and 4.5 fb, for charged Higgs boson masses ranging from 180 GeV to 1000 GeV. In the context of different scenarios of the Minimal Supersymmetric Standard Model, these results exclude nearly all values of tanβ above one for charged Higgs boson masses between 80 GeV and 160 GeV, and exclude a region of parameter space with high tanβ for H± masses between 200 GeV and 250 GeV. .
316. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for anomalous production of prompt like-sign lepton pairs at √s=8 TeV using the ATLAS detector, JHEP, 10.1007/JHEP03(2015)041, 2015, 03, 041, 2015.03, A low-background inclusive search for new physics in events with same-sign dileptons is presented. The search uses proton-proton collisions corresponding to 20.3 fb−1 of integrated luminosity taken in 2012 at a centre-of-mass energy of 8 TeV with the ATLAS detector at the LHC. Pairs of isolated leptons with the same electric charge and large transverse momenta of the type e±e±,e±μ±, and μ±μ± are selected and their invariant mass distribution is examined. No excess of events above the expected level of Standard Model background is found. The results are used to set upper limits on the cross-sections for processes beyond the Standard Model. Limits are placed as a function of the dilepton invariant mass within a fiducial region corresponding to the signal event selection criteria. Exclusion limits are also derived for a specific model of doubly charged Higgs boson production. .
317. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Performance of the ATLAS muon trigger in pp collisions at √s=8 TeV, Eur. Phys. J. C, 10.1140/epjc/s10052-015-3325-9, 75, 120, 2015.03, The performance of the ATLAS muon trigger system is evaluated with proton-proton collision data collected in 2012 at the Large Hadron Collider at a centre-of-mass energy of 8 TeV. It is primarily evaluated using events containing a pair of muons from the decay of Z bosons. The efficiency of the single-muon trigger is measured for muons with transverse momentum 25 < pT < 100 GeV, with a statistical uncertainty of less than 0.01% and a systematic uncertainty of 0.6%. The pT range for efficiency determination is extended by using muons from decays of J/ψ mesons, W bosons, and top quarks. The muon trigger shows highly uniform and stable performance. The performance is compared to the prediction of a detailed simulation. .
318. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena in the dijet mass distribution in ATLAS 2012 data using pp collisions at √s=8 TeV, Phys. Rev. D, 10.1103/PhysRevD.91.052007, 91, 052007, 2015.03, Dijet events produced in LHC proton--proton collisions at a center-of-mass energy √s=8 TeV are studied with the ATLAS detector using the full 2012 data set, with an integrated luminosity of 20.3 fb−1. Dijet masses up to about 4.5 TeV are probed. No resonance-like features are observed in the dijet mass spectrum. Limits on the cross section times acceptance are set at the 95% credibility level for various hypotheses of new phenomena in terms of mass or energy scale, as appropriate. This analysis excludes excited quarks with a mass below 4.09 TeV, color-octet scalars with a mass below 2.72 TeV, heavy W′ bosons with a mass below 2.45 TeV, chiral W∗ bosons with a mass below 1.75 TeV, and quantum black holes with six extra space-time dimensions with threshold mass below 5.82 TeV..
319. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Simultaneous measurements of the top quark pair, W+W-, and Z/gamma* → tau tau production cross sections in pp collisions with the ATLAS detector at √s=7 TeV , Phys. Rev. D, 10.1103/PhysRevD.91.052005, 91, 052005, 2015.03, Simultaneous measurements of the tt¯, W+W−, and Z/γ∗→ττ production cross-sections using an integrated luminosity of 4.6fb−1 of pp collisions at √s=7TeV collected by the ATLAS detector at the LHC are presented. Events are selected with two high transverse momentum leptons consisting of an oppositely charged electron and muon pair. The three processes are separated using the distributions of the missing transverse momentum of events with zero and greater than zero jet multiplicities. Measurements of the fiducial cross-section are presented along with results that quantify for the first time the underlying correlations in the predicted and measured cross-sections due to proton parton distribution functions. These results indicate that the correlated NLO predictions for tt¯ and Z/γ∗→ττ underestimate the data, while those at NNLO generally describe the data well. The full cross-sections are measured to be σ(tt¯)=181.2±2.8+9.7−9.5±3.3±3.3pb, σ(W+W−)=53.3±2.7+7.3−8.0±1.0±0.5pb, and σ(Z/γ∗→ττ)=1174±24+72−87±21±9pb, where the cited uncertainties are due to statistics, systematic effects, luminosity and the LHC beam energy measurement, respectively. The W+W− measurement includes the small contribution from Higgs boson decays, H→W+W−. .
320. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for pair-produced long-lived neutral particles decaying to jets in the ATLAS hadronic calorimeter in pp collisions at sqrt(s) = 8 TeV, Phys. Lett. B, 10.1016/j.physletb.2015.02.015, 743, 15-34, 2015.02, The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3 fb−1 of data collected in proton--proton collisions at √s = 8 TeV. This search is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeV to 900 GeV, and a long-lived neutral particle mass from 10 GeV to 150 GeV. .
321. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the transverse polarization of Λ; and anti-Λ; hyperons produced in proton-proton collisions at √s=7 TeV using the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.91.032004, 91, 032004, 2015.02, The transverse polarization of Λ and Λ¯ hyperons produced in proton-proton collisions at a center-of-mass energy of 7 TeV is measured. The analysis uses 760 μb−1 of minimum bias data collected by the ATLAS detector at the LHC in the year 2010. The measured transverse polarization averaged over Feynman xF from 5×10−5 to 0.01 and transverse momentum pT from 0.8 to 15 GeV is −0.010±0.005(stat)±0.004(syst) for Λ and 0.002±0.006(stat)±0.004(syst) for Λ¯. It is also measured as a function of xF and pT, but no significant dependence on these variables is observed. Prior to this measurement, the polarization was measured at fixed-target experiments with center-of-mass energies up to about 40 GeV. The ATLAS results are compatible with the extrapolation of a fit from previous measurements to the xF range covered by this mesurement. .
322. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of the nuclear modification factor for jets in Pb+Pb collisions at sqrt{NN}=2.76 TeV with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.114.072302, 114, 072302, 2015.02, Measurements of inclusive jet production are performed in pp and Pb+Pb collisions at √sNN=2.76 TeV with the ATLAS detector at the LHC, corresponding to integrated luminosities of 4.0 pb−1 and 0.14 nb−1, respectively. The jets are identified with the anti-kt algorithm with R=0.4, and the spectra are measured over the kinematic range of jet transverse momentum 32
323. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the inclusive jet cross-section in proton--proton collisions at s√=7 TeV using 4.5 fb−1 of data with the ATLAS detector , JHEP, 10.1007/JHEP02(2015)153, 2015, 02, 153, 2015.02, Measurement of the inclusive jet cross-section in proton--proton collisions at s√=7~TeV using 4.5~fb−1 of data with the ATLAS detector .
324. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for invisible particles produced in association with single-top-quarks in proton-proton collisions at √s = 8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-014-3233-4, 75, 79, 2015.02, A search for the production of single-top-quarks in association with missing energy is performed in proton--proton collisions at a centre-of-mass energy of s√ = 8 TeV with the ATLAS experiment at the Large Hadron Collider using data collected in 2012, corresponding to an integrated luminosity of 20.3 fb−1. In this search, the W boson from the top quark is required to decay into an electron or a muon and a neutrino. No deviation from the Standard Model prediction is observed, and upper limits are set on the production cross-section for resonant and non-resonant production of an invisible exotic state in association with a right-handed top quark. In the case of resonant production, for a spin-0 resonance with a mass of 500 GeV, an effective coupling strength above 0.15 is excluded at 95% confidence level for the top quark and an invisible spin-1/2 state with mass between 0 GeV and 100 GeV. In the case of non-resonant production, an effective coupling strength above 0.2 is excluded at 95% confidence level for the top quark and an invisible spin-1 state with mass between 0 GeV and 657 GeV. .
325. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for dark matter in events with heavy quarks and missing transverse momentum in pp collisions with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-015-3306-z, 75, 92, 2015.02, This article reports on a search for dark matter pair production in association with bottom or top quarks in 20.3 fb−1 of pp collisions collected at √s=8 TeV by the ATLAS detector at the LHC. Events with large missing transverse momentum are selected when produced in association with high-momentum jets of which one or more are identified as jets containing b-quarks. Final states with top quarks are selected by requiring a high jet multiplicity and in some cases a single lepton. The data are found to be consistent with the Standard Model expectations and limits are set on the mass scale of effective field theories that describe scalar and tensor interactions between dark matter and Standard Model particles. Limits on the dark-matter--nucleon cross-section for spin-independent and spin-dependent interactions are also provided. These limits are particularly strong for low-mass dark matter. Using a simplified model, constraints are set on the mass of dark matter and of a coloured mediator suitable to explain a possible signal of annihilating dark matter. .
326. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of the W production cross sections in association with jets with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3262-7, 75, 82, 2015.02, This paper presents cross sections for the production of a W boson in association with jets, measured in proton--proton collisions at √s=7 TeV with the ATLAS experiment at the Large Hadron Collider. With an integrated luminosity of 4.6fb−1, this data set allows for an exploration of a large kinematic range, including jet production up to a transverse momentum of 1 TeV and multiplicities up to seven associated jets. The production cross sections for W bosons are measured in both the electron and muon decay channels. Differential cross sections for many observables are also presented including measurements of the jet observables such as the rapidities and the transverse momenta as well as measurements of event observables such as the scalar sums of the transverse momenta of the jets. The measurements are compared to numerous QCD predictions including next-to-leading-order perturbative calculations, resummation calculations and Monte Carlo generators. .
327. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for resonant diboson production in the ℓℓqq final state in pp collisions at sqrt{s}=8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-015-3261-8, 75, 69, 2015.02, This paper reports on a search for narrow resonances in diboson production in the ℓℓqq¯ final state using pp collision data corresponding to an integrated luminosity of 20 fb−1 collected at √s=8 TeV with the ATLAS detector at the Large Hadron Collider. No significant excess of data events over the Standard Model expectation is observed. Upper limits at the 95% confidence level are set on the production cross section times branching ratio for Kaluza--Klein gravitons predicted by the Randall--Sundrum model and for Extended Gauge Model W' bosons. These results lead to the exclusion of mass values below 740 GeV and 1590 GeV for the graviton and W' boson respectively. .
328. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Higgs Boson Pair Production in the γγbb¯ Final State using pp Collision Data at √s=8 TeV from the ATLAS Detector, Phys. Rev. Lett., 10.1103/PhysRevLett.114.081802, 114, 081802, 2015.02, Searches are performed for resonant and non-resonant Higgs boson pair production in the hh→γγbb¯ final state using 20 fb−1 of proton--proton collisions at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the CERN Large Hadron Collider. A 95% confidence level upper limit on the cross section times branching ratio of non-resonant production is set at 2.2 pb, while the expected limit is 1.0 pb. The corresponding limit observed for a narrow resonance ranges between 0.7 and 3.5 pb as a function of its mass. .
329. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of Higgs boson production and couplings in the four-lepton channel in pp collisions at center-of-mass energies of 7 and 8 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.91.012006, 91, 012006, 2015.01, The final ATLAS Run 1 measurements of Higgs boson production and couplings in the decay channel H→ZZ∗→ℓ+ℓ−ℓ′+ℓ′−, where ℓ,ℓ′=e or μ, are presented. These measurements were performed using pp collision data corresponding to integrated luminosities of 4.5 fb−1 and 20.3 fb−1 at center-of-mass energies of 7 TeV and 8 TeV, respectively, recorded with the ATLAS detector at the LHC. The H→ZZ∗→4ℓ signal is observed with a significance of 8.1 standard deviations, with an expectation of 6.2 standard deviations, at mH = 125.36 GeV, the combined ATLAS measurement of the Higgs boson mass from the H→γγ and H→ZZ∗→4ℓ channels. The production rate relative to the Standard Model expectation, the signal strength, is measured in four different production categories in the H→ZZ∗→4ℓ channel. The measured signal strength, at this mass, and with all categories combined, is 1.44 +0.40−0.33. The signal strength for Higgs boson production in gluon fusion or in association with tt¯ or bb¯ pairs is found to be 1.7 +0.5−0.4, while the signal strength for vector-boson fusion combined with WH/ZH associated production is found to be 0.3 +1.6−0.9. .
330. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the production and lepton charge asymmetry of W bosons in Pb+Pb collisions at sqrt(s_NN) = 2.76 TeV with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-014-3231-6, 75, 23, 2015.01, A measurement of W boson production in lead-lead collisions at √sNN=2.76 TeV is presented. It is based on the analysis of data collected with the ATLAS detector at the LHC in 2011 corresponding to an integrated luminosity of 0.14 nb−1 and 0.15 nb−1 in the muon and electron decay channels, respectively. The differential production yields and lepton charge asymmetry are each measured as a function of the average number of participating nucleons and absolute pseudorapidity of the charged lepton. The results are compared to predictions based on next-to-leading-order QCD calculations. These measurements are, in principle, sensitive to possible nuclear modifications to the parton distribution functions and also provide information on scaling of W boson production in multi-nucleon systems. .
331. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Searches for heavy long-lived charged particles with the ATLAS detector in proton-proton collisions at sqrt(s) = 8 TeV, JHEP, 10.1007/JHEP01(2015)068, 2015, 01, 068, 2015.01, Searches for heavy long-lived charged particles are performed using a data sample of 19.8 fb−1 from proton-proton collisions at a centre-of-mass energy of √s = 8 TeV collected by the ATLAS detector at the Large Hadron Collider. No excess is observed above the estimated background and limits are placed on the mass of long-lived particles in various supersymmetric models. Long-lived tau sleptons in models with gauge-mediated symmetry breaking are excluded up to masses between 440 and 385 GeV for tanβ between 10 and 50, with a 290 GeV limit in the case where only direct tau slepton production is considered. In the context of simplified LeptoSUSY models, where sleptons are stable and have a mass of 300 GeV, squark and gluino masses are excluded up to a mass of 1500 and 1360 GeV, respectively. Directly produced charginos, in simplified models where they are nearly degenerate to the lightest neutralino, are excluded up to a mass of 620 GeV. R-hadrons, composites containing a gluino, bottom squark or top squark, are excluded up to a mass of 1270, 845 and 900 GeV, respectively, using the full detector; and up to a mass of 1260, 835 and 870 GeV using an approach disregarding information from the muon spectrometer. .
332. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena in events with a photon and missing transverse momentum in pp collisions at √s=8 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.91.012008, 91, 012008, 2015.01, Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum with the ATLAS experiment at the LHC are reported. Data were collected in proton--proton collisions at a center-of-mass energy of 8 TeV and correspond to an integrated luminosity of 20.3 fb−1. The observed data are well described by the expected Standard Model backgrounds. The expected (observed) upper limit on the fiducial cross section for the production of such events is 6.1 (5.3) fb at 95% confidence level. Exclusion limits are presented on models of new phenomena with large extra spatial dimensions, supersymmetric quarks, and direct pair production of dark-matter candidates..
333. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the WW+WZ cross section and limits on anomalous triple gauge couplings using final states with one lepton, missing transverse momentum, and two jets with the ATLAS detector at sqrt(s) = 7 TeV, JHEP, 10.1007/JHEP01(2015)049, 2015, 01, 049, 2015.01, Measurement of the WW+WZ cross section and limits on anomalous triple gauge couplings using final states with one lepton, missing transverse momentum, and two jets with the ATLAS detector at sqrt(s) = 7 TeV.
334. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Xb and other hidden-beauty states in the π+π−Υ(1S) channel at ATLAS, Phys. Lett. B, 10.1016/j.physletb.2014.11.055, 740, 199-217, 2015.01, This Letter presents a search for a hidden-beauty counterpart of the X(3872) in the mass ranges 10.05--10.31 GeV and 10.40--11.00 GeV, in the channel Xb→π+π−Υ(1S)(→μ+μ−), using 16.2 fb−1 of s√=8 TeV pp collision data collected by the ATLAS detector at the LHC. No evidence for new narrow states is found, and upper limits are set on the product of the Xb cross section and branching fraction, relative to those of the Υ(2S), at the 95% confidence level using the CLS approach. These limits range from 0.8% to 4.0%, depending on mass. For masses above 10.1 GeV, the expected upper limits from this analysis are the most restrictive to date. Searches for production of the Υ(13DJ), Υ(10860), and Υ(11020) states also reveal no significant signals..
335. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for s-channel single top-quark production in proton-proton collisions at √s=8 TeV with the ATLAS detector , Phys. Lett. B, 10.1016/j.physletb.2014.11.042, 740, 118-136, 2015.01, This Letter presents a search at the LHC for s-channel single top-quark production in proton-proton collisions at a centre-of-mass energy of 8 TeV. The analyzed data set was recorded by the ATLAS detector and corresponds to an integrated luminosity of 20.3 fb−1. Selected events contain one charged lepton, large missing transverse momentum and exactly two b-tagged jets. A multivariate event classifier based on boosted decision trees is developed to discriminate s-channel single top-quark events from the main background contributions. The signal extraction is based on a binned maximum-likelihood fit of the output classifier distribution. The analysis leads to an upper limit on the s-channel single top-quark production cross-section of 14.6 pb at the 95% confidence level. The fit gives a cross-section of σs=5.0±4.3 pb, consistent with the Standard Model expectation. .
336. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the bbbar decay of the Standard Model Higgs boson in associated (W/Z)H production with the ATLAS detector, JHEP, 10.1007/JHEP01(2015)069, 2015, 01, 069, 2015.01, A search for the bb¯ decay of the Standard Model Higgs boson is performed with the ATLAS experiment using the full dataset recorded at the LHC in Run 1. The integrated luminosities used from pp collisions at √s=7 and 8 TeV are 4.7 and 20.3 fb−1, respectively. The processes considered are associated (W/Z)H production, where W→eν/μν, Z→ee/μμ and Z→νν. The observed (expected) deviation from the background-only hypothesis corresponds to a significance of 1.4 (2.6) standard deviations and the ratio of the measured signal yield to the Standard Model expectation is found to be μ=0.52±0.32(stat.)±0.24(syst.) for a Higgs boson mass of 125.36 GeV. The analysis procedure is validated by a measurement of the yield of (W/Z)Z production with Z→bb¯ in the same final states as for the Higgs boson search, from which the ratio of the observed signal yield to the Standard Model expectation is found to be 0.74±0.09(stat.)±0.14(syst.). .
337. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for H→γγ produced in association with top quarks and constraints on the Yukawa coupling between the top quark and the Higgs boson using data taken at 7 TeV and 8 TeV with the ATLAS detector , Phys. Lett. B, 10.1016/j.physletb.2014.11.049, 740, 222-242, 2015.01, A search is performed for Higgs bosons produced in association with top quarks using the diphoton decay mode of the Higgs boson. Selection requirements are optimized separately for leptonic and fully hadronic final states from the top quark decays. The dataset used corresponds to an integrated luminosity of 4.5 fb−1 of proton-proton collisions at a center-of-mass energy of 7 TeV and 20.3 fb−1 at 8 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. No significant excess over the background prediction is observed and upper limits are set on the tt¯H production cross section. The observed exclusion upper limit at 95% confidence level is 6.7 times the predicted Standard Model cross section value. In addition, limits are set on the strength of the Yukawa coupling between the top quark and the Higgs boson, taking into account the dependence of the tt¯H and tH cross sections as well as the H→γγ branching fraction on the Yukawa coupling. Lower and upper limits at 95% confidence level are set at -1.3 and +8.0 times the Yukawa coupling strength in the Standard Model. .
338. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the top--anti-top production cross-section as a function of jet multiplicity and jet transverse momentum produced in 7 TeV proton--proton collisions with the ATLAS detector, JHEP, 10.1007/JHEP01(2015)020, 2015, 01, 020, 2015.01, The tt¯ production cross-section dependence on jet multiplicity and jet transverse momentum is reported for proton--proton collisions at a centre-of-mass energy of 7 TeV in the single-lepton channel. The data were collected with the ATLAS detector at the CERN Large Hadron Collider and comprise the full 2011 data sample corresponding to an integrated luminosity of 4.6 fb−1. Differential cross-sections are presented as a function of the jet multiplicity for up to eight jets using jet transverse momentum thresholds of 25, 40, 60, and 80 GeV, and as a function of jet transverse momentum up to the fifth jet. The results are shown after background subtraction and corrections for all detector effects, within a kinematic range closely matched to the experimental acceptance. Several QCD-based Monte Carlo models are compared with the results. Sensitivity to the parton shower modelling is found at the higher jet multiplicities, at high transverse momentum of the leading jet and in the transverse momentum spectrum of the fifth leading jet. The MC@NLO+HERWIG MC is found to predict too few events at higher jet multiplicities. .
339. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Jet energy measurement and its systematic uncertainty in proton--proton collisions at √s=7~TeV with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-014-3190-y, 75, 17, 2015.01, The jet energy scale (JES) and its systematic uncertainty are determined for jets measured with the ATLAS detector using proton-proton collision data with a centre-of-mass energy of s√=7 TeV corresponding to an integrated luminosity of 4.7 fb−1. Jets are reconstructed from energy deposits forming topological clusters of calorimeter cells using the anti-kt algorithm with distance parameters R=0.4 or R=0.6, and are calibrated using MC simulations. A residual JES correction is applied to account for differences between data and MC simulations. This correction and its systematic uncertainty are estimated using a combination of in situ techniques exploiting the transverse momentum balance between a jet and a reference object such as a photon or a Z boson, for 201 TeV. The calibration of forward jets is derived from dijet pT balance measurements. The resulting uncertainty reaches its largest value of 6 for low-pT jets at |η|=4.5. Additional JES uncertainties due to specific event topologies, such as close-by jets or selections of event samples with an enhanced content of jets originating from light quarks or gluons, are also discussed. The magnitude of these uncertainties depends on the event sample used in a given physics analysis, but typically amounts to 0.5 to 3. .
340. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for non-pointing photons in the diphoton and MET final state in √s = 8 TeV pp collisions using the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.90.112005, 90, 112005, 2014.12, A search has been performed, using the full 20.3 fb−1 data sample of 8 TeV proton--proton collisions collected in 2012 with the ATLAS detector at the LHC, for photons originating from a displaced vertex due to the decay of a neutral long-lived particle into a photon and an invisible particle. The analysis investigates the diphoton plus missing transverse momentum final state, and is therefore most sensitive to pair-production of long-lived particles. The analysis technique exploits the capabilities of the ATLAS electromagnetic calorimeter to make precise measurements of the flight direction, as well as the time of flight, of photons. No excess is observed over the Standard Model predictions for background. Exclusion limits are set within the context of Gauge Mediated Supersymmetry Breaking models, with the lightest neutralino being the next-to-lightest supersymmetric particle and decaying into a photon and gravitino with a lifetime in the range from 250 ps to about 100 ns. .
341. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of distributions sensitive to the underlying event in inclusive Z-boson production in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-014-3195-6, 74, 3195, 2014.12, A measurement of charged-particle distributions sensitive to the properties of the underlying event is presented for an inclusive sample of events containing a Z-boson , decaying to an electron or muon pair. The measurement is based on data collected using the ATLAS detector at the LHC in proton-proton collisions at a centre-of-mass energy of 7 TeV with an integrated luminosity of 4.6 fb−1. Distributions of the charged particle multiplicity and of the charged particle transverse momentum are measured in regions of azimuthal angle defined with respect to the Z-boson direction. The measured distributions are compared to similar distributions measured in jet events, and to the predictions of various Monte Carlo generators implementing different underlying event models. .
342. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of Higgs boson production in the diphoton decay channel in pp collisions at center-of-mass energies of 7 and 8 TeV with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.90.112015, 90, 112015, 2014.12, A measurement of the production processes of the recently discovered Higgs boson is performed in the two-photon final state using 5.4 fb−1 of proton-proton collisions data at s√=7 TeV and 20.3 fb−1 at s√=8 TeV collected by the ATLAS detector at the Large Hadron Collider. The number of observed Higgs boson decays to diphotons divided by the corresponding Standard Model prediction, called the signal strength, is found to be μ=1.17±0.27 at the value of the Higgs boson mass measured by ATLAS, mH = 125.4 GeV. The analysis is optimized to measure the signal strengths for individual Higgs boson production processes at this value of mH. They are found to be μggF=1.32±0.38, μVBF=0.8±0.7, μWH=1.0±1.6, μZH=0.1+3.7−0.1, μtt¯H=1.6+2.7−1.8, for Higgs boson production through gluon fusion, vector-boson fusion, and in association with a W or Z boson or a top-quark pair, respectively. Compared with the previously published ATLAS analysis, the results reported here also benefit from a new energy calibration procedure for photons and the subsequent reduction of the systematic uncertainty on the diphoton mass resolution. No significant deviations from the predictions of the Standard Model are found. .
343. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A measurement of the ratio of the production cross sections for W and Z bosons in association with jets with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-014-3168-9, 74, 3168, 2014.12, The ratio of the production cross sections for W and Z bosons in association with jets has been measured in proton-proton collisions at √s = 7 TeV with the ATLAS experiment at the Large Hadron Collider. The measurement is based on the entire 2011 dataset, corresponding to an integrated luminosity of 4.6 fb−1. Inclusive and differential cross-section ratios for massive vector bosons decaying to electrons and muons are measured in association with jets with transverse momentum pT > 30 GeV and jet rapidity |y| < 4.4. The measurements are compared to next-to-leading-order perturbative QCD calculations and to predictions from different Monte Carlo generators implementing leading-order matrix elements supplemented by parton showers. .
344. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the total cross section from elastic scattering in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector, Nucl. Phys. B, 10.1016/j.nuclphysb.2014.10.019, 889, 486-548, 2014.12, A measurement of the total pp cross section at the LHC at s√=7 TeV is presented. In a special run with high-β⋆ beam optics, an integrated luminosity of 80 μb−1 was accumulated in order to measure the differential elastic cross section as a function of the Mandelstam momentum transfer variable t. The measurement is performed with the ALFA sub-detector of ATLAS. Using a fit to the differential elastic cross section in the |t| range from 0.01 GeV2 to 0.1 GeV2 to extrapolate to |t|→0, the total cross section, σtot(pp→X), is measured via the optical theorem to be:σtot(pp→X)=95.35±0.38(stat.)±1.25(exp.)±0.37(extr.)mb,where the first error is statistical, the second accounts for all experimental systematic uncertainties and the last is related to uncertainties in the extrapolation to |t|→0. In addition, the slope of the elastic cross section at small |t| is determined to be B=19.73±0.14(stat.)±0.26(syst.)GeV−2. .
345. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of spin correlation in top-antitop quark events from proton-proton collisions at √s=7 TeV using the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.90.112016, 90, 112016, 2014.12, Measurements of spin correlation in top quark pair production are presented using data collected with the ATLAS detector at the LHC with proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 4.6 fb−1. Events are selected in final states with two charged leptons and at least two jets and in final states with one charged lepton and at least four jets. Four different observables sensitive to different properties of the top quark pair production mechanism are used to extract the correlation between the top and antitop quark spins. Some of these observables are measured for the first time. The measurements are in good agreement with the Standard Model prediction at next-to-leading-order accuracy. .
346. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for contact interactions and large extra dimensions in the dilepton channel using proton-proton collisions at sqrt(s) = 8 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-014-3134-6, 74, 3134, 2014.12, A search is conducted for non-resonant new phenomena in dielectron and dimuon final states, originating from either contact interactions or large extra spatial dimensions. The LHC 2012 proton-proton collision dataset recorded by the ATLAS detector is used, corresponding to 20 fb−1 at √s = 8 TeV. The dilepton invariant mass spectrum is a discriminating variable in both searches, with the contact interaction search additionally utilizing the dilepton forward-backward asymmetry. No significant deviations from the Standard Model expectation are observed. Lower limits are set on the ℓℓqq contact interaction scale Λ between 15.4 TeV and 26.3 TeV, at the 95% credibility level. For large extra spatial dimensions, lower limits are set on the string scale MS between 3.2 TeV to 5.0 TeV. .
347. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Comprehensive measurements of t-channel single top-quark production cross sections at sqrt(s) = 7 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.90.112006, 90, 112006, 2014.12, This article presents measurements of the t-channel single top-quark (t) and top-antiquark (t¯) total production cross sections σ(tq) and σ(t¯q), their ratio Rt=σ(tq)/σ(t¯q), and a measurement of the inclusive production cross section σ(tq+t¯q) in proton--proton collisions at s√=7 TeV at the LHC. Differential cross sections for the tq and t¯q processes are measured as a function of the transverse momentum and the absolute value of the rapidity of t and t¯, respectively. The analyzed data set was recorded with the ATLAS detector and corresponds to an integrated luminosity of 4.59 fb−1. Selected events contain one charged lepton, large missing transverse momentum, and two or three jets. The cross sections are measured by performing a binned maximum-likelihood fit to the output distributions of neural networks. The resulting measurements are σ(tq)=46±6pb, σ(t¯q)=23±4pb, Rt=2.04±0.18, and σ(tq+t¯q)=68±8pb, consistent with the Standard Model expectation. The uncertainty on the measured cross sections is dominated by systematic uncertainties, while the uncertainty on Rt is mainly statistical. Using the ratio of σ(tq+t¯q) to its theoretical prediction, and assuming that the top-quark-related CKM matrix elements obey the relation |Vtb|≫|Vts|,|Vtd|, we determine |Vtb|=1.02±0.07. .
348. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of inclusive jet charged particle fragmentation functions in Pb+Pb collisions at √sNN= 2.76 TeV with the ATLAS detector , Phys. Lett. B, 10.1016/j.physletb.2014.10.065, 739, 320-342, 2014.12, Measurements of charged-particle fragmentation functions of jets produced in ultra-relativistic nuclear collisions can provide insight into the modification of parton showers in the hot, dense medium created in the collisions. ATLAS has measured jets in √sNN=2.76 TeV Pb+Pb collisions at the LHC using a data set recorded in 2011 with an integrated luminosity of 0.14 nb−1. Jets were reconstructed using the anti-kt algorithm with distance parameter values R = 0.2, 0.3, and 0.4. Distributions of charged-particle transverse momentum and longitudinal momentum fraction are reported for seven bins in collision centrality for R=0.4 jets with pjetT>100 GeV. Commensurate minimum pT values are used for the other radii. Ratios of fragment distributions in each centrality bin to those measured in the most peripheral bin are presented. These ratios show a reduction of fragment yield in central collisions relative to peripheral collisions at intermediate z values, 0.04≲z≲0.2 and an enhancement in fragment yield for z≲0.04. A smaller, less significant enhancement is observed at large z and large pT in central collisions. .
349. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for neutral Higgs bosons of the minimal supersymmetric standard model in pp collisions at √s = 8 TeV with the ATLAS detector, JHEP, 10.1007/JHEP11(2014)056, 2014, 11, 056, 2014.11, A search for the neutral Higgs bosons predicted by the Minimal Supersymmetric Standard Model (MSSM) is reported. The analysis is performed on data from proton-proton collisions at a centre-of-mass energy of 8 TeV collected with the ATLAS detector at the Large Hadron Collider. The samples used for this search were collected in 2012 and correspond to integrated luminosities in the range 19.5 - 20.3 fb−1. The MSSM Higgs bosons are searched for in the ττ final state. No significant excess over the expected background is observed, and exclusion limits are derived for the production cross section times branching fraction of a scalar particle as a function of its mass. The results are also interpreted in the MSSM parameter space for various benchmark scenarios. .
350. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for pair and single production of new heavy quarks that decay to a Z boson and a third-generation quark in pp collisions at √s=8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP11(2014)104, 2014, 11, 104, 2014.11, A search is presented for the production of new heavy quarks that decay to a Z boson and a third-generation Standard Model quark. In the case of a new charge +2/3 quark (T), the decay targeted is T→Zt, while the decay targeted for a new charge -1/3 quark (B) is B→Zb. The search is performed with a dataset corresponding to 20.3 fb−1 of pp collisions at s√=8 TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider. Selected events contain a high transverse momentum Z boson candidate reconstructed from a pair of oppositely charged same-flavor leptons (electrons or muons), and are analyzed in two channels defined by the absence or presence of a third lepton. Hadronic jets, in particular those with properties consistent with the decay of a b-hadron, are also required to be present in selected events. Different requirements are made on the jet activity in the event in order to enhance the sensitivity to either heavy quark pair production mediated by the strong interaction, or single production mediated by the electroweak interaction. No significant excess of events above the Standard Model expectation is observed, and lower limits are derived on the mass of vector-like T and B quarks under various branching ratio hypotheses, as well as upper limits on the magnitude of electroweak coupling parameters. .
351. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for long-lived neutral particles decaying into lepton jets in proton-proton collisions at √s = 8 TeV with the ATLAS detector, JHEP, 10.1007/JHEP11(2014)088, 2014, 11, 088, 2014.11, Several models of physics beyond the Standard Model predict neutral particles that decay into final states consisting of collimated jets of light leptons and hadrons (so-called "lepton jets"). These particles can also be long-lived with decay length comparable to, or even larger than, the LHC detectors' linear dimensions. This paper presents the results of a search for lepton jets in proton--proton collisions at the centre-of-mass energy of √s = 8 TeV in a sample of 20.3 fb−1 collected during 2012 with the ATLAS detector at the LHC. Limits on models predicting Higgs boson decays to neutral long-lived lepton jets are derived as a function of the particle's proper decay length. .
352. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of flow harmonics with multi-particle cumulants in Pb+Pb collisions at √sNN=2.76 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-014-3157-z, 74, 3157, 2014.11, ATLAS measurements of the azimuthal anisotropy in lead-lead collisions at √sNN=2.76 TeV are shown using a dataset of approximately 7 μb−1 collected at the LHC in 2010. The measurements are performed for charged particles with transverse momenta 0.5
353. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Fiducial and differential cross sections of Higgs boson production measured in the four-lepton decay channel in pp collisions at √s = 8 TeV with the ATLAS detector , Phys. Lett. B, 10.1016/j.physletb.2014.09.054, 738, 234-253, 2014.11, Measurements of fiducial and differential cross sections of Higgs boson production in the H→ZZ∗→4ℓ decay channel are presented. The cross sections are determined within a fiducial phase space and corrected for detection efficiency and resolution effects. They are based on 20.3 fb−1 of pp collision data, produced at √s=8 TeV centre-of-mass energy at the LHC and recorded by the ATLAS detector. The differential measurements are performed in bins of transverse momentum and rapidity of the four-lepton system, the invariant mass of the subleading lepton pair and the decay angle of the leading lepton pair with respect to the beam line in the four-lepton rest frame, as well as the number of jets and the transverse momentum of the leading jet. The measured cross sections are compared to selected theoretical calculations of the Standard Model expectations. No significant deviation from any of the tested predictions is found. .
354. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new resonances in Wγ and Zγ Final States in pp Collisions at √s=8 TeV with the ATLAS Detector, Phys. Lett. B, 10.1016/j.physletb.2014.10.002, 738, 428-447, 2014.11, This letter presents a search for new resonances decaying to final states with a vector boson produced in association with a high transverse momentum photon, Vγ, with V=W(→ℓν) or Z(→ℓ+ℓ−), where ℓ=e or μ. The measurements use 20.3 fb−1 of proton-proton collision data at a center-of-mass energy of √s=8 TeV recorded with the ATLAS detector. No deviations from the Standard Model expectations are found, and production cross section limits are set at 95% confidence level. Masses of the hypothetical aT and ωT states of a benchmark Low Scale Technicolor model are excluded in the ranges [275,960] GeV and [200,700]∪[750,890] GeV, respectively. Limits at 95% confidence level on the production cross section of a singlet scalar resonance decaying to Zγ final states have also been obtained for masses below 1180 GeV. .
355. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the muon reconstruction performance of the ATLAS detector using 2011 and 2012 LHC proton-proton collision data, Eur. Phys. J. C, 10.1140/epjc/s10052-014-3130-x, 74, 3130, 2014.11, This paper presents the performance of the ATLAS muon reconstruction during the LHC run with pp collisions at √s=7−8 TeV in 2011-2012, focusing mainly on data collected in 2012. Measurements of the reconstruction efficiency and of the momentum scale and resolution, based on large reference samples of J/ψ→μμ, Z→μμ and Υ→μμ decays, are presented and compared to Monte Carlo simulations. Corrections to the simulation, to be used in physics analysis, are provided. Over most of the covered phase space (muon |η|<2.7 and 5≲pT≲100 GeV) the efficiency is above 99% and is measured with per-mille precision. The momentum resolution ranges from 1.7% at central rapidity and for transverse momentum pT≃10 GeV, to 4% at large rapidity and pT≃100 GeV. The momentum scale is known with an uncertainty of 0.05% to 0.2% depending on rapidity. A method for the recovery of final state radiation from the muons is also presented. .
356. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Observation of an excited Bc meson state with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.113.212004, 113, 212004, 2014.11, A search for excited states of the Bc+/- meson is performed using 4.9 inv. fb of 7 TeV and 19.2 inv. fb of 8 TeV pp collision data collected by the ATLAS experiment at the LHC. A new state is observed through its hadronic transition to the ground state, with the latter detected in the decay Bc+/- --> J/psi pi+/-. The state appears in the m(Bc+/- pi+ pi-) - m(Bc+/-) - 2m(pi+/-) mass difference distribution with a significance of 5.2 standard deviations. The mass of the observed state is 6842 +/- 4 +/- 5 MeV, where the first error is statistical and the second is systematic. The mass and decay of this state are consistent with expectations for the second S-wave state of the Bc, Bc(2S). .
357. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the cross-section of high transverse momentum vector bosons reconstructed as single jets and studies of jet substructure in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector, New J. Phys., 10.1088/1367-2630/16/11/113013, 16, 113013 , 2014.11, This paper presents a measurement of the cross-section for high transverse momentum W and Z bosons produced in pp collisions and decaying to all-hadronic final states. The data used in the analysis were recorded by the ATLAS detector at the CERN Large Hadron Collider at a centre-of-mass energy of s√=7 TeV and correspond to an integrated luminosity of 4.6 fb−1. The measurement is performed by reconstructing the boosted W or Z bosons in single jets. The reconstructed jet mass is used to identify the W and Z bosons, and a jet substructure method based on energy cluster information in the jet centre-of-mass frame is used to suppress the large multi-jet background. The cross-section for events with a hadronically decaying W or Z boson, with transverse momentum pT>320GeV and pseudorapidity |η|<1.9, is measured to be σW+Z=8.5±1.7 pb and is compared to the next-to-leading-order calculations. The selected events are further used to study jet grooming techniques. .
358. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for top squark pair production in final states with one isolated lepton, jets, and missing transverse momentum in sqrt(s)=8 TeV pp collisions with the ATLAS detector, JHEP, 10.1007/JHEP11(2014)118, 2014, 11, 118, 2014.11, The results of a search for top squark (stop) pair production in final states with one isolated lepton, jets, and missing transverse momentum are reported. The analysis is performed with proton--proton collision data at √s=8 TeV collected with the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of 20 fb−1. The lightest supersymmetric particle (LSP) is taken to be the lightest neutralino which only interacts weakly and is assumed to be stable. The stop decay modes considered are those to a top quark and the LSP as well as to a bottom quark and the lightest chargino, where the chargino decays to the LSP by emitting a W boson. A wide range of scenarios with different mass splittings between the stop, the lightest neutralino and the lightest chargino are considered, including cases where the W bosons or the top quarks are off-shell. Decay modes involving the heavier charginos and neutralinos are addressed using a set of phenomenological models of supersymmetry. No significant excess over the Standard Model prediction is observed. A stop with a mass between 210 and 640 GeV decaying directly to a top quark and a massless LSP is excluded at 95 % confidence level, and in models where the mass of the lightest chargino is twice that of the LSP, stops are excluded at 95 % confidence level up to a mass of 500 GeV for an LSP mass in the range of 100 to 150 GeV. Stringent exclusion limits are also derived for all other stop decay modes considered, and model-independent upper limits are set on the visible cross-section for processes beyond the Standard Model. .
359. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Standard Model Higgs boson decay to mu+mu- with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2014.09.008, 738, 68-86, 2014.11, A search is reported for Higgs boson decay to μ+μ− using data with an integrated luminosity of 24.8 fb−1 collected with the ATLAS detector in pp collisions at √s=7 and 8 TeV at the CERN Large Hadron Collider. The observed dimuon invariant mass distribution is consistent with the Standard Model background-only hypothesis in the 120-150 GeV search range. For a Higgs boson with a mass of 125.5 GeV, the observed (expected) upper limit at the 95 % confidence level is 7.0 (7.2) times the Standard Model expectation. This corresponds to an upper limit on the branching ratio BR(H→μ+μ−) of 1.5×10−3. .
360. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the cross section of high transverse momentum Z→bb¯ production in proton--proton collisions at sqrt{s}=8 TeV with the ATLAS Detector , Phys. Lett. B, 10.1016/j.physletb.2014.09.020, 738, 25-43, 2014.11, This Letter reports the observation of a high transverse momentum Z→bb¯ signal in proton-proton collisions at s√=8 TeV and the measurement of its production cross section. The data analysed were collected in 2012 with the ATLAS detector at the LHC and correspond to an integrated luminosity of 19.5 fb−1. The Z→bb¯ decay is reconstructed from a pair of b-tagged jets, clustered with the anti-kt jet algorithm with R=0.4, that have low angular separation and form a dijet with pT>200 GeV. The signal yield is extracted from a fit to the dijet invariant mass distribution, with the dominant, multi-jet background mass shape estimated by employing a fully data-driven technique that reduces the dependence of the analysis on simulation. The fiducial cross section is determined to be σfidZ→bb¯=2.02±0.20(stat.)±0.25(syst.)±0.06(lumi.)pb=2.02±0.33pb, in good agreement with next-to-leading-order theoretical predictions. .
361. K. Francis, K. Kawagoe et al. (The CALICE collaboration), Performance of the first prototype of the CALICE scintillator strip electromagnetic calorimeter, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 10.1010/j.nima.2014.06.039, 763, 278-289, 2014.11.
362. K. Motohashi, K. Kawagoe et al., Evaluation of KEK n-in-p planar pixel sensor structures for very high radiation environments with testbeam, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 10.1016/j.nima.2014.05.092, 765, 125-129, 2014.11.
363. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of long-range pseudorapidity correlations and azimuthal harmonics in sqrt(s_NN) = 5.02 TeV proton-lead collisions with the ATLAS detector , Phys. Rev. C, 10.1103/PhysRevC.90.044906, 90, 044906, 2014.10, Measurements of two-particle correlation functions and the first five azimuthal harmonics, v1 to v5, are presented, using 28 nb−1 of p+Pb collisions at a nucleon-nucleon center-of-mass energy of √sNN=5.02 TeV measured with the ATLAS detector at the LHC. Significant long-range ``ridge-like'' correlations are observed for pairs with small relative azimuthal angle (|Δϕ|<π/3) and back-to-back pairs (|Δϕ|>2π/3) over the transverse momentum range 0.44 GeV. The v2(pT), v3(pT) and v4(pT) are compared to the vn coefficients in Pb+Pb collisions at √sNN=2.76 TeV with similar event multiplicities. Reasonable agreement is observed after accounting for the difference in the average pT of particles produced in the two collision systems. .
364. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the lepton flavor violating decay Z → emu in pp collisions at √s=8 TeV with the ATLAS detector , Phys. Rev. D, 10.1103/PhysRevD.90.072010, 90, 072010, 2014.10, The ATLAS detector at the Large Hadron Collider is used to search for the lepton flavor violating process Z→eμ in pp collisions using 20.3 fb−1 of data collected at √s = 8 TeV. An enhancement in the eμ invariant mass spectrum is searched for at the Z boson mass. The number of Z bosons produced in the data sample is estimated using events of similar topology, Z→ee and μμ, significantly reducing the systematic uncertainty in the measurement. There is no evidence of an enhancement at the Z boson mass, resulting in an upper limit on the branching fraction, B(Z→eμ) < 7.5 x 10−7 at the 95% confidence level. .
365. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Scalar Diphoton Resonances in the Mass Range 65-600 GeV with the ATLAS Detector in pp Collision Data at √s = 8 TeV, Phys. Rev. Lett., 10.1103/PhysRevLett.113.171801, 113, 171801, 2014.10, A search for scalar particles decaying via narrow resonances into two photons in the mass range 65−600 GeV is performed using 20.3 fb−1 of √s = 8 TeV pp collision data collected with the ATLAS detector at the Large Hadron Collider. The recently discovered Higgs boson is treated as a background. No significant evidence for an additional signal is observed. The results are presented as limits at the 95 % confidence level on the production cross-section of a scalar boson times branching ratio into two photons, in a fiducial volume where the reconstruction efficiency is approximately independent of the event topology. The upper limits set extend over a considerably wider mass range than previous searches. .
366. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of jet vetoes and azimuthal decorrelations in dijet events produced in pp collisions at √s = 7 TeV using the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-014-3117-7, 74, 3117, 2014.10, Additional jet activity in dijet events is measured using pp collisions at ATLAS at a centre-of-mass energy of 7 TeV, for jets reconstructed using the anti-kt algorithm with radius parameter R=0.6. This is done using variables such as the fraction of dijet events without an additional jet in the rapidity interval bounded by the dijet subsystem and correlations between the azimuthal angles of the dijets. They are presented, both with and without a veto on additional jet activity in the rapidity interval, as a function of the mean transverse momentum of the dijets and of the rapidity interval size. The double differential dijet cross section is also measured as a function of the interval size and the azimuthal angle between the dijets. These variables probe differences in the approach to resummation of large logarithms when performing QCD calculations. The data are compared to POWHEG, interfaced to the PYTHIA 8 and HERWIG parton shower generators, as well as to HEJ with and without interfacing it to the ARIADNE parton shower generator. None of the theoretical predictions agree with the data across the full phase-space considered; however, POWHEG+PYTHIA 8 and HEJ+ARIADNE are found to provide the best agreement with the data.These measurements use the full data sample collected with the ATLAS detector in 7 TeV pp collisions at the LHC and correspond to integrated luminosities of 36.1 pb−1 and 4.5 fb−1 for data collected during 2010 and 2011 respectively. .
367. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Electron and photon energy calibration with the ATLAS detector using LHC Run 1 data, Eur. Phys. J. C, 10.1140/epjc/s10052-014-3071-4, 74, 3071, 2014.10, This paper presents the electron and photon energy calibration achieved with the ATLAS detector using about 25 fb−1 of LHC proton--proton collision data taken at centre-of-mass energies of √s = 7 and 8 TeV. The reconstruction of electron and photon energies is optimised using multivariate algorithms. The response of the calorimeter layers is equalised in data and simulation, and the longitudinal profile of the electromagnetic showers is exploited to estimate the passive material in front of the calorimeter and reoptimise the detector simulation. After all corrections, the Z resonance is used to set the absolute energy scale. For electrons from Z decays, the achieved calibration is typically accurate to 0.05% in most of the detector acceptance, rising to 0.2% in regions with large amounts of passive material. The remaining inaccuracy is less than 0.2-1% for electrons with a transverse energy of 10 GeV, and is on average 0.3% for photons. The detector resolution is determined with a relative inaccuracy of less than 10% for electrons and photons up to 60 GeV transverse energy, rising to 40% for transverse energies above 500 GeV. .
368. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of differential production cross-sections for a Z boson in association with b-jets in 7 TeV proton-proton collisions with the ATLAS detector, JHEP, 10.1007/JHEP10(2014)141, 2014, 10, 141, 2014.10, Measurements of differential production cross-sections of a Z boson in association with b-jets in pp collisions at √s=7 TeV are reported. The data analysed correspond to an integrated luminosity of 4.6 fb−1 recorded with the ATLAS detector at the Large Hadron Collider. Particle-level cross-sections are determined for events with a Z boson decaying into an electron or muon pair, and containing b-jets. For events with at least one b-jet, the cross-section is presented as a function of the Z boson transverse momentum and rapidity, together with the inclusive b-jet cross-section as a function of b-jet transverse momentum, rapidity and angular separations between the b-jet and the Z boson. For events with at least two b-jets, the cross-section is determined as a function of the invariant mass and angular separation of the two highest transverse momentum b-jets, and as a function of the Z boson transverse momentum and rapidity. Results are compared to leading-order and next-to-leading-order perturbative QCD calculations. .
369. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for strong production of supersymmetric particles in final states with missing transverse momentum and at least three b-jets at sqrt(s) = 8 TeV proton-proton collisions with the ATLAS detector, JHEP, 10.1007/JHEP10(2014)024, 2014, 10, 024, 2014.10, This paper reports the results of a search for strong production of supersymmetric particles in 20.1 fb−1 of proton-proton collisions at a centre-of-mass energy of 8 TeV using the ATLAS detector at the LHC. The search is performed separately in events with either zero or at least one high pT lepton (electron or muon), large missing transverse momentum, high jet multiplicity and at least three jets identified as originated from the fragmentation of a b-quark. No excess is observed with respect to the Standard Model predictions. The results are interpreted in the context of several supersymmetric models involving gluinos and scalar top and bottom quarks, as well as a mSUGRA/CMSSM model. Gluino masses up to 1340 GeV are excluded, depending on the model, significantly extending the previous ATLAS limits. .
370. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of top-quark pair differential cross-sections in the l+jets channel in pp collisions at √s = 7 TeV using the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.90.072004, 90, 072004, 2014.10, Measurements of normalized differential cross-sections for top-quark pair production are presented as a function of the top-quark transverse momentum, and of the mass, transverse momentum, and rapidity of the ttbar system, in proton--proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV. The dataset corresponds to an integrated luminosity of 4.6 fb^-1, recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. Events are selected in the lepton+jets channel, requiring exactly one lepton and at least four jets with at least one of the jets tagged as originating from a b-quark. The measured spectra are corrected for detector efficiency and resolution effects and are compared to several Monte Carlo simulations and theory calculations. The results are in fair agreement with the predictions in a wide kinematic range. Nevertheless, data distributions are softer than predicted for higher values of the mass of the ttbar system and of the top-quark transverse momentum. The measurements can also discriminate among different sets of parton distribution functions. .
371. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the direct production of charginos, neutralinos and staus in final states with at least two hadronically decaying taus and missing transverse momentum in pp collisions at √s = 8 TeV with the ATLAS detector, JHEP, 10.1007/JHEP10(2014)096, 2014, 10, 096, 2014.10, Results of a search for the electroweak associated production of charginos and next-to-lightest neutralinos, pairs of charginos or pairs of tau sleptons are presented. These processes are characterised by final states with at least two hadronically decaying tau leptons, missing transverse momentum and low jet activity. The analysis is based on an integrated luminosity of 20.3 fb−1 of proton--proton collisions at √s=8 TeV recorded with the ATLAS experiment at the Large Hadron Collider. No significant excess is observed with respect to the predictions from Standard Model processes. Limits are set at 95% confidence level on the masses of the lighter chargino and next-to-lightest neutralino for various hypotheses for the lightest neutralino mass in simplified models. In the scenario of direct production of chargino pairs, with each chargino decaying into the lightest neutralino via an intermediate tau slepton, chargino masses up to 345 GeV are excluded for a massless lightest neutralino. For associated production of mass-degenerate charginos and next-to-lightest neutralinos, both decaying into the lightest neutralino via an intermediate tau slepton, masses up to 410 GeV are excluded for a massless lightest neutralino. .
372. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the ttˉ production cross-section using eμ events with b-tagged jets in pp collisions at √s=7 and 8 TeV with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-014-3109-7, 74, 3109, 2014.10, The inclusive top quark pair production cross-section has been measured in proton-proton collisions at sqrt(s)=7 TeV and sqrt(s)=8 TeV with the ATLAS experiment at the LHC, using ttbar events with an opposite-charge e-mu pair in the final state. The measurement was performed with the 2011 7 TeV dataset corresponding to an integrated luminosity of 4.6 fb-1 and the 2012 8 TeV dataset of 20.3 fb-1. The numbers of events with exactly one and exactly two b-tagged jets were counted and used to simultaneously determine sigma(ttbar) and the efficiency to reconstruct and b-tag a b-jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section was measured to be: sigma(ttbar)=182.9±3.1±4.2±3.6±3.3 pb (7 TeV) and sigma(ttbar)=242.4±1.7±5.5±7.5±4.2 pb (8 TeV), where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the knowledge of the integrated luminosity and of the LHC beam energy. The results are consistent with recent theoretical QCD calculations at NNLO. Fiducial measurements corresponding to the experimental acceptance of the leptons are also reported, together with the ratio of cross-sections measured at the two centre-of-mass energies. The inclusive cross-section results were used to determine the top quark pole mass via the dependence of the theoretically-predicted cross-section on mpolet, giving a result of mpolet=172.9+2.5−2.6 GeV. By looking for an excess of ttbar production with respect to the QCD prediction, the results were also used to place limits on the pair-production of supersymmetric top squarks with masses close to the top quark mass decaying to predominantly right-handed top quarks and a light neutralino, the lightest supersymmetric particle. Top squarks with masses between the top quark mass and 177 GeV are excluded at the 95% confidence level. .
373. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for WZ resonances in the fully leptonic channel using pp collisions at sqrt(s) = 8 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2014.08.039, 737, 223-243, 2014.10, A search for resonant WZ production in the lnul'l' (l, l'= e,mu) decay channel using 20.3 fb-1 of sqrt(s) = 8 TeV pp collision data collected by the ATLAS experiment at LHC is presented. No significant deviation from the Standard Model prediction is observed and upper limits on the production cross sections of WZ resonances from an extended gauge model W' and from a simplified model of heavy vector triplets are derived. A corresponding observed (expected) lower mass limit of 1.52 (1.49) TeV is derived for the W' at the 95% confidence level. .
374. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Evidence of electroweak production of WWjj In pp collisions at √s=8 TeV with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.113.141803, 113, 141803 , 2014.10, This Letter presents the first study of W±W±jj, same-electric-charge diboson production in association with two jets, using 20.3 fb−1 of proton--proton collision data at √s=8 TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with two reconstructed same-charge leptons (e±e±, e±μ±, and μ±μ±) and two or more jets are analyzed. Production cross sections are measured in two fiducial regions, with different sensitivities to the electroweak and strong production mechanisms. First evidence for W±W±jj production and electroweak-only W±W±jj production is observed with a significance of 4.5 and 3.6 standard deviations respectively. The measured production cross sections are in agreement with Standard Model predictions. Limits at 95% confidence level are set on anomalous quartic gauge couplings. .
375. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new particles in events with one lepton and missing transverse momentum in pp collisions at √s = 8 TeV with the ATLAS detector , JHEP, 10.1007/JHEP09(2014)037, 2014, 09, 037, 2014.09, This paper presents a search for new particles in events with one lepton (electron or muon) and missing transverse momentum using 20.3 fb−1 of proton-proton collision data at √s=8 TeV recorded by the ATLAS experiment at the Large Hadron Collider. No significant excess beyond Standard Model expectations is observed. A W′ with Sequential Standard Model couplings is excluded at the 95% confidence level for masses up to 3.24 TeV. Excited chiral bosons (W∗) with equivalent coupling strengths are excluded for masses up to 3.21 TeV. In the framework of an effective field theory limits are also set on the dark matter-nucleon scattering cross-section as well as the mass scale M∗ of the unknown mediating interaction for dark matter pair production in association with a leptonically decaying W. .
376. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the production cross-section of psi(2S) -> J/psi -> mu+mu-pi+pi- in pp collisions at sqrt(s) = 7 TeV at ATLAS , JHEP, 10.1007/JHEP09(2014)079, 2014, 09, 079, 2014.09, The prompt and non-prompt production cross-sections for ψ(2S) mesons are measured using 2.1 fb−1 of pp collision data at a centre-of-mass energy of 7 TeV recorded by the ATLAS experiment at the LHC. The measurement exploits the ψ(2S)→J/ψ(→μ+μ−)π+π− decay mode, and probes ψ(2S) mesons with transverse momenta in the range 10≤pT<100 GeV and rapidity |y|<2.0. The results are compared to other measurements of ψ(2S) production at the LHC and to various theoretical models for prompt and non-prompt quarkonium production. .
377. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of fiducial and differential cross sections for Higgs boson production in the diphoton decay channel at sqrt(s) = 8 TeV with ATLAS , JHEP, 10.1007/JHEP09(2014)112, 2014, 09, 112, 2014.09, Measurements of fiducial and differential cross sections are presented for Higgs boson production in proton-proton collisions at a centre-of-mass energy of √s=8 TeV. The analysis is performed in the H→γγ decay channel using 20.3 fb−1 of data recorded by the ATLAS experiment at the CERN Large Hadron Collider. The signal is extracted using a fit to the diphoton invariant mass spectrum assuming that the width of the resonance is much smaller than the experimental resolution. The signal yields are corrected for the effects of detector inefficiency and resolution. The pp→H→γγ fiducial cross section is measured to be 43.2±9.4(stat)+3.2−2.9(syst)±1.2(lumi) fb for a Higgs boson of mass 125.4 GeV decaying to two isolated photons that have transverse momentum greater than 35% and 25% of the diphoton invariant mass and each with absolute pseudorapidity less than 2.37. Four additional fiducial cross sections and two cross-section limits are presented in phase space regions that test the theoretical modelling of different Higgs boson production mechanisms, or are sensitive to physics beyond the Standard Model. Differential cross sections are also presented, as a function of variables related to the diphoton kinematics and the jet activity produced in the Higgs boson events. The observed spectra are statistically limited but broadly in line with the theoretical expectations. .
378. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Flavour tagged time dependent angular analysis of the Bs→J/ψ phi decay and extraction of Delta Gammas and the weak phase phis in ATLAS , Phys. Rev. D, 10.1103/PhysRevD.90.052007, 90, 052007 , 2014.09, A measurement of the Bs→J/ψϕ decay parameters, updated to include flavour tagging is reported using 4.9fb−1 of integrated luminosity collected by the ATLAS detector from s√=7TeV pp collisions recorded in 2011 at the LHC. The values measured for the physical parameters are: ϕsΔΓΓs|A∥(0)|2|A0(0)|2δ⊥======0.12±0.25(stat.)±0.05(syst.)rad0.053±0.021(stat.)0.010(syst.)ps−10.677±0.007(stat.)±0.004(syst.)ps−10.220±0.008(stat.)±0.009(syst.)0.529±0.006(stat.)±0.012(syst.)3.89±0.47(stat.)±0.11(syst.)rad where the parameter ΔΓ is constrained to be positive. The S-wave contribution was measured and found to be compatible with zero. Results for ϕs and ΔΓ are also presented as 68% and 95% likelihood contours, which show agreement with the Standard Model expectations. .
379. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for supersymmetry in events with large missing transverse momentum, jets, and at least one tau lepton in 20 fb-1 of √s= 8 TeV proton-proton collision data with the ATLAS detector, JHEP, 10.1007/JHEP09(2014)103, 2014, 09, 103, 2014.09, A search for supersymmetry (SUSY) in events with large missing transverse momentum, jets, at least one hadronically decaying tau lepton and zero or one additional light leptons (electron/muon), has been performed using 20.3 fb−1 of proton-proton collision data at √s=8 TeV recorded with the ATLAS detector at the Large Hadron Collider. No excess above the Standard Model background expectation is observed in the various signal regions and 95% confidence level upper limits on the visible cross section for new phenomena are set. The results of the analysis are interpreted in several SUSY scenarios, significantly extending previous limits obtained in the same final states. In the framework of minimal gauge-mediated SUSY breaking models, values of the SUSY breaking scale Λ below 63 TeV are excluded, independently of tanβ. Exclusion limits are also derived for an mSUGRA/CMSSM model, in both the R-parity-conserving and R-parity-violating case. A further interpretation is presented in a framework of natural gauge mediation, in which the gluino is assumed to be the only light coloured sparticle and gluino masses below 1090 GeV are excluded. .
380. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for pair-produced third-generation squarks decaying via charm quarks or in compressed supersymmetric scenarios in pp collisions at √s=8 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.90.052008, 90, 052008, 2014.09, Results of a search for supersymmetry via direct production of third-generation squarks are reported, using 20.3 fb−1 of proton-proton collision data at √s=8 TeV recorded by the ATLAS experiment at the LHC in 2012. Two different analysis strategies based on monojet-like and c-tagged event selections are carried out to optimize the sensitivity for direct top squark pair production in the decay channel to a charm quark and the lightest neutralino (t~1→c+χ~01) across the top squark--neutralino mass parameter space. No excess above the Standard Model background expectation is observed. The results are interpreted in the context of direct pair production of top squarks and presented in terms of exclusion limits in the (mt~1, mχ~01) parameter space. A top squark of mass up to about 240 GeV is excluded at 95% confidence level for arbitrary neutralino masses, within the kinematic boundaries. Top squark masses up to 270 GeV are excluded for a neutralino mass of 200 GeV. In a scenario where the top squark and the lightest neutralino are nearly degenerate in mass, top squark masses up to 260 GeV are excluded. The results from the monojet-like analysis are also interpreted in terms of compressed scenarios for top squark pair production in the decay channel t~1→b+ff′+χ~01 and sbottom pair production with b~1→b+χ~01, leading to a similar exclusion for nearly mass-degenerate third-generation squarks and the lightest neutralino. The results in this paper significantly extend previous results at colliders. .
381. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A neural network clustering algorithm for the ATLAS silicon pixel detector, JINST, 10.1088/1748-0221/9/09/P09009, 9, P09009, 2014.09, A novel technique to identify and split clusters created by multiple charged particles in the ATLAS pixel detector using a set of artificial neural networks is presented. Such merged clusters are a common feature of tracks originating from highly energetic objects, such as jets. Neural networks are trained using Monte Carlo samples produced with a detailed detector simulation. This technique replaces the former clustering approach based on a connected component analysis and charge interpolation. The performance of the neural network splitting technique is quantified using data from proton--proton collisions at the LHC collected by the ATLAS detector in 2011 and from Monte Carlo simulations. This technique reduces the number of clusters shared between tracks in highly energetic jets by up to a factor of three. It also provides more precise position and error estimates of the clusters in both the transverse and longitudinal impact parameter resolution. .
382. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the Higgs boson mass from the H→γγ and H→ZZ∗→4ℓ channels with the ATLAS detector at the LHC , Phys. Rev. D, 10.1103/PhysRevD.90.052004, 90, 052004, 2014.09, An improved measurement of the mass of the Higgs boson is derived from a combined fit to the invariant mass spectra of the decay channels H→γγ and H→ZZ∗→4ℓ. The analysis uses the pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at center-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of 25 fb−1. The measured value of the Higgs boson mass is mH = 125.36 ± 0.37 (stat) ± 0.18 (syst) GeV. This result is based on improved energy-scale calibrations for photons, electrons, and muons as well as other analysis improvements, and supersedes the previous result from ATLAS. Upper limits on the total width of the Higgs boson are derived from fits to the invariant mass spectra of the H→γγ and H→ZZ∗→4ℓ decay channels. .
383. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the Z/γ∗ boson transverse momentum distribution in pp collisions at √s = 7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP09(2014)145, 2014, 09, 145, 2014.09, This paper describes a measurement of the Z/γ∗ boson transverse momentum spectrum using ATLAS proton-proton collision data at a centre-of-mass energy of √s = 7 TeV at the LHC. The measurement is performed in the Z/γ∗→e+e− and Z/γ∗→μ+μ− channels, using data corresponding to an integrated luminosity of 4.7 fb−1. Normalized differential cross sections as a function of the Z/γ∗ boson transverse momentum are measured for transverse momenta up to 800 GeV. The measurement is performed inclusively for Z/γ∗ rapidities up to 2.4, as well as in three rapidity bins. The channel results are combined, compared to perturbative and resummed QCD calculations and used to constrain the parton shower parameters of Monte Carlo generators. .
384. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for direct pair production of the top squark in all-hadronic final states in proton--proton collisions at √s=8~TeV with the ATLAS detector , JHEP, 10.1007/JHEP09(2014)015, 2014, 09, 015, 2014.09, The results of a search for direct pair production of the scalar partner to the top quark using an integrated luminosity of 20.1fb−1 of proton-proton collision data at s√=8 TeV recorded with the ATLAS detector at the LHC are reported. The top squark is assumed to decay via t~→tχ~01 or t~→bχ~±1→bW(∗)χ~01, where χ~01 (χ~±1) denotes the lightest neutralino (chargino) in supersymmetric models. The search targets a fully-hadronic final state in events with four or more jets and large missing transverse momentum. No significant excess over the Standard Model background prediction is observed, and exclusion limits are reported in terms of the top squark and neutralino masses and as a function of the branching fraction of t~→tχ~01. For a branching fraction of 100%, top squark masses in the range 270-645 GeV are excluded for χ~01 masses below 30 GeV. For a branching fraction of 50% to either t~→tχ~01 or t~→bχ~±1, and assuming the χ~±1 mass to be twice the χ~01 mass, top squark masses in the range 250-550 GeV are excluded for χ~01 masses below 60 GeV. .
385. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using 20.3 fb−1 of √s=8 TeV proton-proton collision data, JHEP, 10.1007/JHEP09(2014)176, 2014, 09, 176, 2014.09, A search for squarks and gluinos in final states containing high-pT jets, missing transverse momentum and no electrons or muons is presented. The data were recorded in 2012 by the ATLAS experiment in √s=8 TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of 20.3fb−1. No significant excess above the Standard Model expectation is observed. Results are interpreted in a variety of simplified and specific supersymmetry-breaking models assuming that R-parity is conserved and that the lightest neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 1330 GeV for a simplified model incorporating only a gluino and the lightest neutralino. For a simplified model involving the strong production of first- and second-generation squarks, squark masses below 850 GeV (440 GeV) are excluded for a massless lightest neutralino, assuming mass degenerate (single light-flavour) squarks. In mSUGRA/CMSSM models with tanβ=30, A0=−2m0 and μ>0, squarks and gluinos of equal mass are excluded for masses below 1700 GeV. Additional limits are set for non-universal Higgs mass models with gaugino mediation and for simplified models involving the pair production of gluinos, each decaying to a top squark and a top quark, with the top squark decaying to a charm quark and a neutralino. These limits extend the region of supersymmetric parameter space excluded by previous searches with the ATLAS detector. .
386. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for supersymmetry in events with four or more leptons in √s = 8 TeV pp collisions with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.90.05200, 90, 052001, 2014.09, Results from a search for supersymmetry in events with four or more leptons including electrons, muons and taus are presented. The analysis uses a data sample corresponding to 20.3 fb−1 of proton--proton collisions delivered by the Large Hadron Collider at √s = 8 TeV and recorded by the ATLAS detector. Signal regions are designed to target supersymmetric scenarios that can be either enriched in or depleted of events involving the production of a Z boson. No significant deviations are observed in data from Standard Model predictions and results are used to set upper limits on the event yields from processes beyond the Standard Model. Exclusion limits at the 95% confidence level on the masses of relevant supersymmetric particles are obtained. In R-parity-violating simplified models with decays of the lightest supersymmetric particle to electrons and muons, limits of 1350 GeV and 750 GeV are placed on gluino and chargino masses, respectively. In R-parity-conserving simplified models with heavy neutralinos decaying to a massless lightest supersymmetric particle, heavy neutralino masses up to 620 GeV are excluded. Limits are also placed on other supersymmetric scenarios. .
387. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for High-Mass Dilepton Resonances in pp Collisions at √s = 8 TeV with the ATLAS Detector, Phys. Rev. D, 10.1103/PhysRevD.90.052005, 90, 052005, 2014.09, The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to dielectron or dimuon final states. Results are presented from an analysis of proton-proton (pp) collisions at a center-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb-1 in the dielectron channel and 20.5 fb-1 in the dimuon channel. A narrow resonance with Standard Model Z couplings to fermions is excluded at 95% confidence level for masses less than 2.79 TeV in the dielectron channel, 2.53 TeV in the dimuon channel, and 2.90 TeV in the two channels combined. Limits on other model interpretations are also presented, including a grand-unification model based on the E6 gauge group, Z* bosons, Minimal Z' Models, a spin-2 graviton excitation from Randall-Sundrum models, quantum black holes and a Minimal Walking Technicolor model with a composite Higgs boson..
388. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Muon Reconstruction Efficiency and Momentum Resolution of the ATLAS Experiment in Proton-Proton Collisions at √s = 7 TeV in 2010, Eur. Phys. J. C, 10.1140/epjc/s10052-014-3034-9, 74, 3034, 2014.09, This paper presents a study of the performance of the muon reconstruction in the analysis of proton-proton collisions at √s=7 TeV at the LHC, recorded by the ATLAS detector in 2010. This performance is described in terms of reconstruction and isolation efficiencies and momentum resolutions for different classes of reconstructed muons. The results are obtained from an analysis of J/ψ meson and Z boson decays to dimuons, reconstructed from a data sample corresponding to an integrated luminosity of 40~pb−1. The measured performance is compared to Monte Carlo predictions and deviations from the predicted performance are discussed..
389. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the underlying event in jet events from 7 TeV proton-proton collisions with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-014-2965-5, 74, 2965, 2014.08, Distributions sensitive to the underlying event in QCD jet events have been measured with the ATLAS detector at the LHC, based on 37/pb of proton-proton collision data collected at a centre-of-mass energy of 7 TeV. Charged-particle mean pT and densities of all-particle ET and charged-particle multiplicity and pT have been measured in regions azimuthally transverse to the hardest jet in each event. These are presented both as one-dimensional distributions and with their mean values as functions of the leading-jet transverse momentum from 20 GeV to 800 GeV. The correlation of charged-particle mean pT with charged-particle multiplicity is also studied, and the ET densities include the forward rapidity region; these features provide extra data constraints for Monte Carlo modelling of colour reconnection and beam-remnant effects respectively. For the first time, underlying event observables have been computed separately for inclusive jet and exclusive dijet event selections, allowing more detailed study of the interplay of multiple partonic scattering and QCD radiation contributions to the underlying event. Comparisons to the predictions of different Monte Carlo models show a need for further model tuning, but the standard approach is found to generally reproduce the features of the underlying event in both types of event selection..
390. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Light-quark and gluon jet discrimination in pp collisions at sqrt(s)=7 TeV with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-014-3023-z, 74, 3023, 2014.08, A likelihood-based discriminant for the identification of quark- and gluon-initiated jets is built and validated using 4.7 fb−1 of proton-proton collision data at √s = 7 TeV collected with the ATLAS detector at the LHC. Data samples with enriched quark or gluon content are used in the construction and validation of templates of jet properties that are the input to the likelihood-based discriminant. The discriminating power of the jet tagger is established in both data and Monte Carlo samples within a systematic uncertainty of 10-20%. In data, light-quark jets can be tagged with an efficiency of 50% while achieving a gluon-jet mis-tag rate of 25% in a pT range between 40 GeV and 360 GeV for jets in the acceptance of the tracker. The rejection of gluon-jets found in the data is significantly below what is attainable using a Pythia 6 Monte Carlo simulation, where gluon-jet mis-tag rates of 10% can be reached for a 50% selection efficiency of light-quark jets using the same jet properties. .
391. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for microscopic black holes and string balls in final states with leptons and jets with the ATLAS detector at √s=8 TeV, JHEP, 10.1007/JHEP08(2014)103, 2014, 08, 103, 2014.08, A search for an excess of events with multiple high transverse momentum objects including charged leptons and jets is presented, using 20.3 fb^-1 of proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2012 at a centre-of-mass energy of sqrt(s) = 8 TeV. No excess of events beyond Standard Model expectations is observed. Using extra-dimensional models for black hole and string ball production and decay, exclusion contours are determined as a function of the mass threshold for production and the fundamental gravity scale for two, four and six extra dimensions. For six extra dimensions, mass thresholds of 4.8-6.2 TeV are excluded at 95% confidence level, depending on the fundamental gravity scale and model assumptions. Upper limits on the fiducial cross-sections for non-Standard Model production of these final states are set. .
392. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the centrality and pseudorapidity dependence of the integrated elliptic flow in lead-lead collisions at √sNN = 2.76 TeV with the ATLAS detector , Eur. Phys. J. C, 10.1140/epjc/s10052-014-2982-4, 74, 2982, 2014.08, The integrated elliptic flow of charged particles produced in Pb+Pb collisions at sqrt(s_NN)=2.76 TeV has been measured with the ATLAS detector using data collected at the Large Hadron Collider. The anisotropy parameter, v_2, was measured in the pseudorapidity range |eta| <= 2.5 with the event-plane method. In order to include tracks with very low transverse momentum pT, thus reducing the uncertainty in v_2 integrated over pT, a 1 mu b-1 data sample without a magnetic field in the tracking detectors is used. The centrality dependence of the integrated v_2 is compared to other measurements obtained with higher pT thresholds. A weak pseudorapidity dependence of the integrated elliptic flow is observed for central collisions, and a small decrease when moving away from mid-rapidity is observed only in peripheral collisions. The integrated v2 transformed to the rest frame of one of the colliding nuclei is compared to the lower-energy RHIC data. .
393. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Operation and performance of the ATLAS semiconductor tracker, JINST, 10.1088/1748-0221/9/08/P08009, 9, P08009, 2014.08, The semiconductor tracker is a silicon microstrip detector forming part of the inner tracking system of the ATLAS experiment at the LHC. The operation and performance of the semiconductor tracker during the first years of LHC running are described. More than 99% of the detector modules were operational during this period, with an average intrinsic hit efficiency of (99.74 +/- 0.04)%. The evolution of the noise occupancy is discussed, and measurements of the Lorentz angle, delta-ray production and energy loss presented. The alignment of the detector is found to be stable at the few-micron level over long periods of time. Radiation damage measurements, which include the evolution of detector leakage currents, are found to be consistent with predictions and are used in the verification of radiation background simulations..
394. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of event-plane correlations in √sNN = 2.76 TeV lead-lead collisions with the ATLAS detector , Phys. Rev. C, 10.1103/PhysRevC.90.024905, 90, 024905, 2014.08, A measurement of event-plane correlations involving two or three event planes of different order is presented as a function of centrality for 7 ub-1 Pb+Pb collision data at sqrt(s_NN)=2.76 TeV, recorded by the ATLAS experiment at the LHC. Fourteen correlators are measured using a standard event-plane method and a scalar-product method, and the latter method is found to give a systematically larger correlation signal. Several different trends in the centrality dependence of these correlators are observed. These trends are not reproduced by predictions based on the Glauber model, which includes only the correlations from the collision geometry in the initial state. Calculations that include the final-state collective dynamics are able to describe qualitatively, and in some cases also quantitatively, the centrality dependence of the measured correlators. These observations suggest that both the fluctuations in the initial geometry and non-linear mixing between different harmonics in the final state are important for creating these correlations in momentum space. .
395. C. Adloff, K. Kawagoe et al. (The CALICE collaboration), The time structure of hadronic showers in highly granular calorimeters with tungsten and steel absorbers, JOURNAL OF INSTRUMENTATION, 10.1088/1748-0221/9/07/P07022, 9, 2014.07.
396. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), The differential production cross section of the phi(1020) meson in √s = 7 TeV pp collisions measured with the ATLAS Detector, Eur. Phys. J. C, 10.1140/epjc/s10052-014-2895-2, 74, 2895, 2014.07, A measurement is presented of the phi to K+K- production cross section at sqrt(s) = 7 TeV using pp collision data corresponding to an integrated luminosity of 383 mub-1, collected with the ATLAS experiment at the LHC. Selection of phi(1020) mesons is based on the identification of charged kaons by their energy loss in the pixel detector. The differential cross section is measured as a function of the transverse momentum, pTphi, and rapidity, |yphi|, of the phi(1020) meson in the fiducial region 500 < pTphi< 1200 MeV, |yphi| < 0.8, kaon pTK> 230 MeV and kaon momentum pK< 800 MeV.The integrated phi(1020)-meson production cross section in this fiducial range is measured to be s(phi K+K-) = 570 pm 8 (stat) pm 66 (syst) pm 20 (lumi) mub..
397. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Electron reconstruction and identification efficiency measurements with the ATLAS detector using the 2011 LHC proton-proton collision data, Eur. Phys. J. C, 10.1140/epjc/s10052-014-2941-0, 74, 2941, 2014.07, Many of the interesting physics processes to be measured at the LHC have a signature involving one or more isolated electrons. The electron reconstruction and identification efficiencies of the ATLAS detector at the LHC have been evaluated using proton-proton collision data collected in 2011 at sqrt(s) = 7 TeV and corresponding to an integrated luminosity of 4.7/fb. Tag-and-probe methods using events with leptonic decays of W and Z bosons and J/psi mesons are employed to benchmark these performance parameters. The combination of all measurements results in identification efficiencies determined with an accuracy at the few per mil level for electron transverse energy greater than 30 GeV..
398. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of chi_c1 and chi_c2 production with √s = 7 TeV pp collisions at ATLAS, JHEP, 10.1007/JHEP07(2014)154, 2014, 07, 154, 2014.07, The prompt and non-prompt production cross-sections for the chi_c1 and chi_c2 charmonium states are measured in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector at the LHC using 4.5 fb^-1 of integrated luminosity. The chi_c states are reconstructed through the radiative decay chi_c -> J/psi gamma (with J/psi -> mu+mu-) where photons are reconstructed from gamma -> e+e- conversions. The production rate of the chi_c2 state relative to the chi_c1 state is measured for prompt and non-prompt chi_c as a function of J/psi transverse momentum. The prompt chi_c cross-sections are combined with existing measurements of prompt J/psi production to derive the fraction of prompt J/psi produced in feed-down from chi_c decays. The fractions of chi_c1 and chi_c2 produced in b-hadron decays are also measured..
399. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), The monitoring and data quality assessment of the ATLAS liquid argon calorimeter, JINST, 10.1088/1748-0221/9/07/P07024, 9, 07, P07024, 2014.07, The liquid argon calorimeter is a key component of the ATLAS detector installed at the CERN Large Hadron Collider. The primary purpose of this calorimeter is the measurement of electrons and photons. It also provides a crucial input for measuring jets and missing transverse momentum. An advanced data monitoring procedure was designed to quickly identify issues that would affect detector performance and ensure that only the best quality data are used for physics analysis. This article presents the validation procedure developed during the 2011 and 2012 LHC data taking periods, in which more than 98% of the proton proton luminosity recorded by ATLAS at a centre-of-mass energy of 7 and 8 TeV had calorimeter data quality suitable for physics analysis..
400. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for dark Matter in events with single Z and missing transverse Energy using pp collisions at √s = 8 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.90.012004, 90, 012004, 2014.07, A search is presented for production of dark matter particles recoiling against a leptonically decaying Z boson in 20.3 fb−1 of pp collisions at √s=8 TeV with the ATLAS detector at the Large Hadron Collider. Events with large missing transverse momentum and two oppositely-charged electrons or muons consistent with the decay of a Z boson are analyzed. No excess above the Standard Model prediction is observed. Limits are set on the mass scale of the contact interaction as a function of the dark matter particle mass using an effective field theory description of the interaction of dark matter with quarks or with Z bosons. Limits are also set on the coupling and mediator mass of a model in which the interaction is mediated by a scalar particle..
401. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the low mass Drell-Yan differential cross section at √s = 7 TeV using the ATLAS detector, JHEP, 10.1007/JHEP06(2014)112, 2014, 06, 112, 2014.06, The differential cross section for the process Z/γ∗→ll (l=e,μ) as a function of dilepton invariant mass is measured in pp collisions at √s= 7 TeV at the LHC using the ATLAS detector. The measurement is performed in the e and μ channels for invariant masses between 26 GeV and 66 GeV using an integrated luminosity of 1.6 fb−1 collected in 2011 and these measurements are combined. The analysis is extended to invariant masses as low as 12 GeV in the muon channel using 35 pb−1 of data collected in 2010. The cross sections are determined within fiducial acceptance regions and corrections to extrapolate the measurements to the full kinematic range are provided. Next-to-next-to-leading-order QCD predictions provide a significantly better description of the results than next-to-leading-order QCD calculations, unless the latter are matched to a parton shower calculation..
402. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for supersymmetry at √s = 8 TeV in final states with jets and two same-sign leptons or three leptons with the ATLAS detector, JHEP, 10.1007/JHEP06(2014)035, 2014, 06, 035, 2014.06, A search for strongly produced supersymmetric particles is conducted using signatures involving multiple energetic jets and either two isolated leptons (e or μ) with the same electric charge, or at least three isolated leptons. The search also utilises jets originating from b-quarks, missing transverse momentum and other observables to extend its sensitivity. The analysis uses a data sample corresponding to a total integrated luminosity of 20.3 fb−1 of √s= 8 TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider in 2012. No deviation from the Standard Model expectation is observed. New or significantly improved exclusion limits are set on a wide variety of supersymmetric models in which the lightest squark can be of the first, second or third generations, and in which R-parity can be conserved or violated..
403. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for direct top squark pair production in final states with two leptons in √s = 8 TeV pp collisions with the ATLAS detector, JHEP, 10.1007/JHEP06(2014)124, 2014, 06, 124, 2014.06, A search is presented for direct top-squark pair production in final states with two leptons (electrons or muons) of opposite charge using 20.3fb-1 of pp collision data at sqrt(s)=8TeV, collected by the ATLAS experiment at the Large Hadron Collider in 2012. No excess over the Standard Model expectation is found. The results are interpreted under the separate assumptions (i) that the top squark decays to a b-quark in addition to an on-shell chargino whose decay occurs via a real or virtual W boson, or (ii) that the top squark decays to a t-quark and the lightest neutralino. A top squark with a mass between 150 GeV and 445 GeV decaying to a b-quark and an on-shell chargino is excluded at 95% confidence level for a top squark mass equal to the chargino mass plus 10 GeV, in the case of a 1 GeV lightest neutralino. Top squarks with masses between 215 (90) GeV and 530 (170) GeV decaying to an on-shell (off-shell) t-quark and a neutralino are excluded at 95% confidence level for a 1 GeV neutralino..
404. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for top quark decays t→ qH with H→γγ using the ATLAS detector, JHEP, 10.1007/JHEP06(2014)008, 2014, 06, 008, 2014.06, A search is performed for flavour-changing neutral currents in the decay of a top quark to an up-type (c,u) quark and a Higgs boson, where the Higgs boson decays to two photons. The proton-proton collision data set used corresponds to 4.7 fb−1 at √s = 7 TeV and 20.3 fb−1 at √s = 8 TeV collected by the ATLAS experiment at the LHC. Top quark pair events are searched for in which one top quark decays to qH and the other decays to bW. Both the hadronic and the leptonic decay modes of the W boson are used. No significant signal is observed and an upper limit is set on the t→qH branching ratio of 0.79% at the 95% confidence level. The corresponding limit on the tqH coupling combination √λ^2_tcH+λ^2_tuH is 0.17..
405. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for direct stop pair production in events with a Z boson, b-jets and missing transverse energy with the ATLAS detector using 21 fb-1 from proton-proton collision at √s =8 TeV, Eur. Phys. J. C, 10.1140/epjc/s10052-014-2883-6, 74, 2883, 2014.06, A search is presented for direct top squark pair production using events with at least two leptons including a same-flavour opposite-sign pair with invariant mass consistent with the Z boson mass, jets tagged as originating from b-quarks and missing transverse momentum. The analysis is performed with proton-proton collision data at √s=8 TeV collected with the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of 20.3 fb−1. No excess beyond the Standard Model expectation is observed. Interpretations of the results are provided in models based on the direct pair production of the heavier top squark state (t~2) followed by the decay to the lighter top squark state (t~1) via t~2→Zt~1, and for t~1 pair production in natural gauge-mediated supersymmetry breaking scenarios where the neutralino (χ~01) is the next-to-lightest supersymmetric particle and decays producing a Z boson and a gravitino (G~) via the χ~01→ZG~ process..
406. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the 4l Cross Section at the Z Resonance and Determination of the Branching Fraction of Z→4l in pp Collisions at √s = 7 and 8 TeV with ATLAS, Phys. Rev. Lett., 10.1103/PhysRevLett.112.231806, 112, 231806, 2014.06, Measurements of four-lepton (4ℓ, ℓ=e,μ) production cross sections at the Z resonance in pp collisions at the LHC with the ATLAS detector are presented. For dilepton and four-lepton invariant mass region mℓ+ℓ−>5 GeV and 80
407. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of dijet cross sections in pp collisions at 7 TeV centre-of-mass energy using the ATLAS detector, JHEP, 10.1007/JHEP05(2014)059, 2014, 05, 059, 2014.05, Double-differential dijet cross sections measured in pp collisions at the LHC with a 7 TeV centre-of-mass energy are presented as functions of dijet mass and rapidity separation of the two highest-pT jets. These measurements are obtained using data corresponding to an integrated luminosity of 4.5/fb, recorded by the ATLAS detector in 2011. The data are corrected for detector effects so that cross sections are presented at the particle level. Cross sections are measured up to 5 TeV dijet mass using jets reconstructed with the anti-kt algorithm for values of the jet radius parameter of 0.4 and 0.6. The cross sections are compared with next-to-leading-order perturbative QCD calculations by NLOJET++ corrected to account for non-perturbative effects. Comparisons with POWHEG predictions, using a next-to-leading-order matrix element calculation interfaced to a parton-shower Monte Carlo simulation, are also shown. Electroweak effects are accounted for in both cases. The quantitative comparison of data and theoretical predictions obtained using various parameterizations of the parton distribution functions is performed using a frequentist method. An example setting a lower limit on the compositeness scale for a model of contact interactions is presented, showing that the unfolded results can be used to constrain contributions to dijet production beyond that predicted by the Standard Model..
408. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Invisible Decays of a Higgs Boson Produced in Association with a Z Boson in ATLAS, Phys. Rev. Lett., 10.1103/PhysRevLett.112.201802, 112, 201802, 2014.05, A search for evidence of invisible-particle decay modes of a Higgs boson produced in association with a Z boson at the Large Hadron Collider is presented. No deviation from the Standard Model expectation is observed in 4.5 fb−1 (20.3 fb−1) of 7 (8) TeV pp collision data collected by the ATLAS experiment. Assuming the Standard Model rate for ZH production, an upper limit of 75%, at the 95% confidence level is set on the branching ratio to invisible-particle decay modes of the Higgs boson at a mass of 125.5 GeV. The limit on the branching ratio is also interpreted in terms of an upper limit on the allowed dark matter--nucleon scattering cross section within a Higgs-portal dark matter scenario. Limits are also set on an additional neutral Higgs boson, in the mass range 110
409. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Standard Model Higgs boson decay to a photon and a Z boson in pp collisions at √s = 7 and 8 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2014.03.015, 732, 8-27, 2014.05, A search is reported for a neutral Higgs boson in the decay channel H->Z gamma, Z->l+l- (l=e, mu), using 4.5 fb-1 of pp collisions at sqrt(s) = 7 TeV and 20.3 fb-1 of pp collisions at sqrt(s) = 8 TeV, recorded by the ATLAS detector at the CERN Large Hadron Collider. The observed distribution of the invariant mass of the three final-state particles, m(llgamma), is consistent with the Standard Model hypothesis in the investigated mass range of 120-150 GeV. For a Higgs boson with a mass of 125.5 GeV, the observed upper limit at the 95% confidence level is 11 times the Standard Model expectation. Upper limits are set on the cross section times branching ratio of a neutral Higgs boson with mass in the range 120-150 GeV between 0.13 and 0.5 pb for sqrt(s)=8 TeV at 95% confidence level..
410. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the parity violating asymmetry parameter αb and the helicity amplitudes for the decay ΛB → J/ψ Λ0 with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.89.092009, 89, 092009, 2014.05, A measurement of the parity-violating decay asymmetry parameter, alpha_b, and the helicity amplitudes for the decay Lambda_b->J/psi(mu mu)+Lambda(p pi) is reported. The analysis is based on 1400 Lambda_b and anti-Lambda_b baryons selected in 4.6/fb of proton-proton collision data with a center-of-mass energy of 7 TeV recorded by the ATLAS experiment at the LHC. By combining the Lambda_b and anti-Lambda_b samples under the assumption of CP conservation, the value of alpha_b is measured to be 0.30+/-0.16(stat)+/-0.06(syst). This measurement provides a test of theoretical models based on perturbative QCD or heavy-quark effective theory..
411. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the production of a W boson in association with a charm quark in pp collisions at √s = 7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP05(2014)068, 2014, 05, 068, 2014.05, The production of a W boson in association with a single charm quark is studied using 4.6 fb^-1 of pp collision data at sqrt(s)=7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96 +0.26 -0.30 at Q^2=1.9 GeV^2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio sigma(W^+ + bar{c})/sigma(W^- + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s-bar{s} quark asymmetry..
412. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Searches for direct production of charginos, neutralinos and sleptons in final states with two leptons and missing transverse momentum in pp collisions at √s = 8TeV with the ATLAS detector, JHEP, 10.1007/JHEP05(2014)071, 2014, 05, 071, 2014.05, Searches for the electroweak production of charginos, neutralinos and sleptons in final states characterized by the presence of two leptons (electrons and muons) and missing transverse momentum are performed using 20.3 fb-1 of proton-proton collision data at sqrt(s) = 8 TeV recorded with the ATLAS experiment at the Large Hadron Collider. No significant excess beyond Standard Model expectations is observed. Limits are set on the masses of the lightest chargino, next-to-lightest neutralino and sleptons for different lightest-neutralino mass hypotheses in simplified models. Results are also interpreted in various scenarios of the phenomenological Minimal Supersymmetric Standard Model..
413. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the production cross-section of prompt J/Psi mesons in association with a W boson in pp collisions at √s = 7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP04(2014)172, 2014, 04, 172, 2014.04, The process pp--> W + J/psi provides a powerful probe of the production mechanism of charmonium in hadronic collisions, and is also sensitive to multiple parton interactions in the colliding protons. Using the 2011 ATLAS dataset of 4.5 fb-1 of sqrt{s} = 7 TeV pp collisions at the LHC, the first observation is made of the production of W + prompt J/psi events in hadronic collisions, using W-->mu+nu and J/psi-->mu+mu. A yield of 27.4+7.5-6.5 W + prompt J/psi events is observed, with a statistical significance of 5.1 sigma. The production rate as a ratio to the inclusive W boson production rate is measured, and the double parton scattering contribution to the cross section is estimated..
414. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the electroweak production of dijets in association with a Z-boson and distributions sensitive to vector boson fusion in proton-proton collisions at √s = 8 TeV using the ATLAS detector, JHEP, 10.1007/JHEP04(2014)031, 2014, 04, 031, 2014.04, Measurements of fiducial cross sections for the electroweak production of two jets in association with a Z-boson are presented. The measurements are performed using 20.3 inverse femtobarns of proton-proton collision data collected at a centre-of-mass energy of sqrt(s)=8 TeV by the ATLAS experiment at the Large Hadron Collider. The electroweak component is extracted by a fit to the dijet invariant mass distribution in a fiducial region chosen to enhance the electroweak contribution over the dominant background in which the jets are produced via the strong interaction. The electroweak cross sections measured in two fiducial regions are in good agreement with the Standard Model expectations and the background-only hypothesis is rejected with significance above the 5 sigma level. The electroweak process includes the vector boson fusion production of a Z-boson and the data are used to place limits on anomalous triple gauge boson couplings. In addition, measurements of cross sections and differential distributions for inclusive Z-boson-plus-dijet production are performed in five fiducial regions, each with different sensitivity to the electroweak contribution. The results are corrected for detector effects and compared to predictions from the SHERPA and POWHEG event generators..
415. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s =8 TeV pp collisions with the ATLAS detector, JHEP, 10.1007/JHEP04(2014)169, 2014, 04, 169, 2014.04, A search for the direct production of charginos and neutralinos in final states with three leptons and missing transverse momentum is presented. The analysis is based on 20.3 fb-1 of sqrt(s) = 8 TeV proton--proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with the Standard Model expectations and limits are set in R-parity-conserving phenomenological Minimal Supersymmetric Standard Models and in simplified supersymmetric models, significantly extending previous results. For simplified supersymmetric models of direct chargino (χ~±1) and next-to-lightest neutralino (χ~02) production with decays to lightest neutralino (χ~01) via either all three generations of sleptons, staus only, gauge bosons, or Higgs bosons, χ~±1 and χ~02 masses are excluded up to 700 GeV, 380 GeV, 345 GeV, or 148 GeV respectively, for a massless χ~01..
416. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A study of heavy-flavor quarks produced in association with top-quark pairs at √s = 7 TeV using the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.89.072012, 89, 072012, 2014.04, Using a sample of dilepton top-quark pair (ttbar) candidate events, a study is performed of the production of top-quark pairs together with heavy-flavor (HF) quarks, ttbar+b+X or ttbar+c+X, collectively referred to as ttbar+HF. The dataset used corresponds to an integrated luminosity of 4.7 fb-1 of proton--proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The presence of additional HF quarks in the ttbar sample is inferred by looking for events with at least three b-tagged jets, where two are attributed to the b-quarks from the ttbar decays and the third to additional HF production. The dominant background to ttbar+HF in this sample is ttbar+jet events in which a light-flavor jet is misidentified as a heavy-flavor jet. To determine the heavy- and light-flavor content of the additional b-tagged jets, a fit to the vertex mass distribution of b-tagged jets in the sample is performed. The result of the fit shows that 79 +/- 14 (stat.) +/- 22 (syst.) of the 105 selected extra b-tagged jets originate from HF quarks, three standard deviations away from the hypothesis of zero ttbar+HF production. The result for extra HF production is quoted as a ratio (R_HF) of the cross section for ttbar+HF production to the cross section for ttbar production with at least one additional jet. Both cross sections are measured in a fiducial kinematic region within the ATLAS acceptance. R_HF is measured to be [6.2 +/- 1.1 (stat.) +/- 1.8 (syst.)]% for jets with pT>25 GeV and |eta|<2.5, in agreement with the expectations from Monte Carlo generators..
417. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Quantum Black-Hole Production in High-Invariant-Mass Lepton+Jet Final States Using Proton-Proton Collisions at √s = 8 TeV and the ATLAS Detector, Phys. Rev. Lett., 10.1103/PhysRevLett.112.091804, 112, 091804, 2014.03, This Letter presents a search for quantum black-hole production using 20.3 inverse fb of data collected with the ATLAS detector in pp collisions at the LHC at sqrt(s) = 8 TeV. The quantum black holes are assumed to decay into a lepton (electron or muon) and a jet. In either channel, no event with a lepton-jet invariant mass of 3.5 TeV or more is observed, consistent with the expected background. Limits are set on the product of cross sections and branching fractions for the lepton+jet final states of quantum black holes produced in a search region for invariant masses above 1 TeV. The combined 95% confidence level upper limit on this product for quantum black holes with threshold mass above 3.5 TeV is 0.18 fb. This limit constrains the threshold quantum black-hole mass to be above 5.3 TeV in the model considered..
418. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the inclusive isolated prompt photon cross section in pp collisions at √s = 7 TeV with the ATLAS detector using 4.6 fb-1, Phys. Rev. D, 10.1103/PhysRevD.89.052004, 89, 052004, 2014.03, A measurement of the cross section for the production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The results are based on an integrated luminosity of 4.6 fb-1 collected with the ATLAS detector at the LHC. The cross section is measured as a function of photon pseudorapidity and transverse energy in the kinematic range between 100 GeV and 1000 GeV and in the regions of pseudorapidity less than 1.37 and between 1.52 and 2.37. The results are compared to leading-order parton-shower Monte Carlo models and next-to-leading-order perturbative QCD calculations. Next-to-leading-order perturbative QCD calculations agree well with the measured cross sections as a function of transverse energy and pseudorapidity..
419. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Standalone Vertex Finding in the ATLAS Muon Spectrometer, JINST, 10.1088/1748-0221/9/02/P02001, 9, 02, P02001, 2014.02, A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bb final states, and pp collision data at sqrt(s) = 7 TeV collected with the ATLAS detector at the LHC during 2011..
420. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a Multi-Higgs Boson Cascade in W+W- bbar events with the ATLAS detector in pp collisions at √s = 8 TeV, Phys. Rev. D, 10.1103/PhysRevD.89.032002, 89, 032002, 2014.02, A search is presented for new particles in an extension to the Standard Model that includes a heavy Higgs boson H0, an intermediate charged Higgs boson pair H+-, and a light Higgs boson h0. The analysis searches for events involving the production of a single heavy neutral Higgs boson which decays to the charged Higgs boson and a W boson, where the charged Higgs boson subsequently decays into a W boson and the lightest neutral Higgs boson decaying to a bottom--antibottom-quark pair. Such a cascade results in a W-boson pair and a bottom--antibottom-quark pair in the final state. Events with exactly one lepton, missing transverse momentum, and at least four jets are selected from a data sample corresponding to an integrated luminosity of 20.3/fb, collected by the ATLAS detector in proton--proton collisions at sort(s)=8 TeV at the LHC. The data are found to be consistent with Standard Model predictions, and 95% confidence-level upper limits are set on the product of cross section and branching ratio. These limits range from 0.065 pb to 43 pb as a function of H0 and H+- masses, with m(h0) fixed at 125 GeV..
421. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the top quark pair production charge asymmetry in proton-proton collisions at √s = 7 TeV using the ATLAS detector, JHEP, 10.1007/JHEP02(2014)107, 2014, 02, 107, 2014.02, This letter presents a measurement of the top quark pair (tt) production charge asymmetry Ac using 4.7 fb-1 of proton-proton collisions at a centre-of-mass energy of 7 TeV collected by the ATLAS detector at the LHC. A tt-enriched sample of events with a single lepton (electron or muon), missing transverse momentum and at least four high transverse momentum jets, of which at least one is tagged as coming from a b-quark, is selected. A likelihood fit is used to reconstruct the tt event kinematics. A Bayesian unfolding procedure is employed to estimate Ac at the parton-level. The measured value of the tt production charge asymmetry is 0.006 +/- 0.010, where the uncertainty includes both the statistical and the systematic components. Differential Ac measurements as a function of the invariant mass, the rapidity and the transverse momentum of the tt-system are also presented. In addition, Ac is measured for a subset of events with large tt velocity, where physics beyond the Standard Model could contribute. All measurements are consistent with the Standard Model predictions..
422. C. Adloff, K. Kawagoe et al. (The CALICE collaboration), Shower development of particles with momenta from 1 to 10 GeV in the CALICE Scintillator-Tungsten HCAL, JOURNAL OF INSTRUMENTATION, 10.1088/1748-0221/9/01/P01004, 9, 2014.01.
423. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the mass difference between top and antitop quarks in pp collisions at √s = 7TeV using the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2013.12.010, 728, 363-379, 2014.01, A measurement of the mass difference between top and anti-top quarks is presented. In a 4.7 fb-1 data sample of proton--proton collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC, events consistent with ttbar production and decay into a single charged lepton final state are reconstructed. For each event, the mass difference between the top and anti-top quark candidate is calculated. A two b-tag requirement is used in order to reduce the background contribution. A maximum likelihood fit to these per-event mass differences yields mt-mtbar = 0.67 +/- 0.61 (stat) +/- 0.41 (syst) GeV, consistent with CPT invariance..
424. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for dark matter in events with a hadronically decaying W or Z boson and missing transverse momentum in pp collisions at √s =8 TeV with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.112.041802, 112, 041802, 2014.01, A search is presented for dark matter pair production in association with a W or Z boson in pp collisions representing 20.3 fb-1 of integrated luminosity at sqrt(s)=8 TeV using data recorded with the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet with the jet-mass consistent with a W or Z boson, and with large missing transverse momentum are analyzed. The data are consistent with the Standard Model expectations, and limits are set on the mass scale in effective field theories that describe the interaction of dark matter and Standard Model particles..
425. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena in photon + jet events collected in proton-proton collisions at √s = 8 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2013.12.029, 728, 562-578, 2014.01, This Letter describes a model-independent search for the production of new resonances in photon + jet events using 20 inverse fb of proton--proton LHC data recorded with the ATLAS detector at a centre-of-mass energy of sqrt(s) = 8 TeV. The photon + jet mass distribution is compared to a background model fit from data; no significant deviation from the background-only hypothesis is found. Limits are set at 95% credibility level on generic Gaussian-shaped signals and two benchmark phenomena beyond the Standard Model: non-thermal quantum black holes and excited quarks. Non-thermal quantum black holes are excluded below masses of 4.6 TeV and excited quarks are excluded below masses of 3.5 TeV..
426. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of top quark polarization in top-antitop events from proton-proton collisions at √s = 7 TeV using the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.111.232002, 111, 232002, 2013.12, This Letter presents measurements of the polarization of the top quark in top-antitop quark pair events, using 4.7 fb^-1 of proton-proton collision data recorded with the ATLAS detector at the Large Hadron Collider at sqrt(s) = 7 TeV. Final states containing one or two isolated leptons (electrons or muons) and jets are considered. Two measurements of alpha_l P, the product of the leptonic spin-analyzing power and the top quark polarization, are performed assuming that the polarization is introduced by either a CP conserving (CPC) or a CP violating (CPV) production process. The measurements obtained, alpha_l P_CPC = -0.035 +/- 0.014 (stat) +/- 0.037 (syst) and alpha_l P_CPV = 0.020 +/- 0.016 (stat) +0.013 -0.017 (syst), are in good agreement with the Standard Model prediction of negligible top quark polarization..
427. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of jet shapes in top-quark pair events at √s =7 TeV using the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-013-2676-3, 73, 2676, 2013.12, A measurement of jet shapes in top-quark pair events using 1.8 fb(-1) of sqrt(s) = 7 TeV pp collision data recorded by the ATLAS detector at the LHC is presented. Samples of top-quark pair events are selected in both the single-lepton and dilepton final states. The differential and integrated shapes of the jets initiated by bottom-quarks from the top-quark decays are compared with those of the jets originated by light-quarks from the hadronic W-boson decays in the single-lepton channel. The light-quark jets are found to have a narrower distribution of the momentum flow inside the jet area than b-quark jets..
428. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for long-lived stopped R-hadrons decaying out-of-time with pp collisions using the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.88.112003, 88, 112003, 2013.12, An updated search is performed for gluino, top squark, or bottom squark R-hadrons that have come to rest within the ATLAS calorimeter, and decay at some later time to hadronic jets and a neutralino, using 5.0 and 22.9 fb-1 of pp collisions at 7 and 8 TeV, respectively. Candidate decay events are triggered in selected empty bunch crossings of the LHC in order to remove pp collision backgrounds. Selections based on jet shape and muon-system activity are applied to discriminate signal events from cosmic ray and beam-halo muon backgrounds. In the absence of an excess of events, improved limits are set on gluino, stop, and sbottom masses for different decays, lifetimes, and neutralino masses. With a neutralino of mass 100 GeV, the analysis excludes gluinos with mass below 832 GeV (with an expected lower limit of 731 GeV), for a gluino lifetime between 10 microseconds and 1000 s in the generic R-hadron model with equal branching ratios for decays to qqbar+neutralino and gluon+neutralino. Under the same assumptions for the neutralino mass and squark lifetime, top squarks and bottom squarks in the Regge R-hadron model are excluded with masses below 379 and 344 GeV, respectively..
429. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for charginos nearly mass-degenerate with the lightest neutralino based on a disappearing-track signature in pp collisions at √s = 8 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.88.112006, 88, 112006, 2013.12, A search is presented for direct chargino production based on a disappearing-track signature using 20.3 fb-1 of proton-proton collisions at sqrt(s) = 8 TeV collected with the ATLAS experiment at the LHC. In anomaly-mediated supersymmetry breaking (AMSB) models, the lightest chargino is nearly mass-degenerate with the lightest neutralino and its lifetime is long enough to be detected in the tracking detectors by identifying decays that result in tracks with no associated hits in the outer region of the tracking system. Some models with supersymmetry also predict charginos with a significant lifetime. This analysis attains sensitivity for charginos with a lifetime between 0.1 ns and 10 ns, and significantly surpasses the reach of the LEP experiments. No significant excess above the background expectation is observed for candidate tracks with large transverse momentum, and constraints on chargino properties are obtained. In the AMSB scenarios, a chargino mass below 270 GeV is excluded at 95% confidence level..
430. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the top quark charge in pp collisions at √s = 7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP11(2013)031, 2013, 11, 031, 2013.11, A measurement of the top quark electric charge is carried out in the ATLAS experiment at the Large Hadron Collider using 2.05 fb-1 of data at a centre-of-mass energy of 7 TeV. In units of the elementary electric charge, the top quark charge is determined to be 0.64 +- 0.02 (stat.) +- 0.08 (syst.) from the charges of the top quark decay products in single lepton ttbar candidate events. This excludes models that propose a heavy quark of electric charge --4/3, instead of the Standard Model top quark, with a significance of more than 8 sigma..
431. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the distributions of event-by-event flow harmonics in Pb+Pb collisions at √sNN = 2.76 TeV with the ATLAS detector, JHEP, 10.1007/JHEP11(2013)183, 2013, 11, 183, 2013.11, The distributions of event-by-event harmonic flow coefficients v_n for n=2-4 are measured in sqrt(s_NN)=2.76 TeV Pb+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using charged particles with transverse momentum pT> 0.5 GeV and in the pseudorapidity range |eta|<2.5 in a dataset of approximately 7 ub^-1 recorded in 2010. The shapes of the v_n distributions are described by a two-dimensional Gaussian function for the underlying flow vector in central collisions for v_2 and over most of the measured centrality range for v_3 and v_4. Significant deviations from this function are observed for v_2 in mid-central and peripheral collisions, and a small deviation is observed for v_3 in mid-central collisions. It is shown that the commonly used multi-particle cumulants are insensitive to the deviations for v_2. The v_n distributions are also measured independently for charged particles with 0.51 GeV. When these distributions are rescaled to the same mean values, the adjusted shapes are found to be nearly the same for these two pT ranges. The v_n distributions are compared with the eccentricity distributions from two models for the initial collision geometry: a Glauber model and a model that includes corrections to the initial geometry due to gluon saturation effects. Both models fail to describe the experimental data consistently over most of the measured centrality range..
432. S. Schael, K. Kawagoe et al. (The ALEPH, DELPHI, L3, OPAL, and LEP Electroweak Collaborations), Electroweak measurements in electron positron collisions at W-boson-pair energies at LEP, PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 10.1016/j.physrep.2013.07.004, 532, 4, 119-244, 2013.11.
433. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Evidence for the spin-0 nature of the Higgs boson using ATLAS data, Phys. Lett. B, 10.1016/j.physletb.2013.08.026, 726, 120-144, 2013.10, Studies of the spin and parity quantum numbers of the Higgs boson are presented, based on proton-proton collision data collected by the ATLAS experiment at the LHC. The Standard Model spin-parity JP=0+ hypothesis is compared with alternative hypotheses using the Higgs boson decays H->gammagamma, H->ZZ*->4l and H->WW*->lnulnu, as well as the combination of these channels. The analysed dataset corresponds to an integrated luminosity of 20.7 fb-1 collected at a centre-of-mass energy of sqrt(s)=8 TeV. For the H->ZZ*->4l decay mode the dataset corresponding to an integrated luminosity of 4.6 fb-1 collected at sqrt(s) is included. The data are compatible with the Standard Model JP=0+ quantum numbers for the Higgs boson, whereas all alternative hypotheses studied in this Letter, namely some specific JP=0-,1+,1-,2+ models, are excluded at confidence levels above 97.8%. This exclusion holds independently of the assumptions on the coupling strengths to the Standard Model particles and in the case of the JP=2+ model, of the relative fractions of gluon-fusion and quark-antiquark production of the spin-2 particle. The data thus provide evidence for the spin-0 nature of the Higgs boson, with positive parity being strongly preferred..
434. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC, Phys. Lett. B, 10.1016/j.physletb.2013.08.010, 726, 88-119, 2013.10, Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H->gammagamma, H->ZZ*->4l and H->WW*->lnulnu. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of sqrt(s)=7 TeV and sqrt(s)=8 TeV, corresponding to an integrated luminosity of about 25 fb-1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson..
435. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena using final states with large jet multiplicities and missing transverse momentum with ATLAS in 20 fb−1 of √s = 8 TeV proton-proton collisions, JHEP, 10.1007/JHEP10(2013)130, 2013, 10, 130, 2013.10, A search is presented for new particles decaying to large numbers (7 to greater or equal to 10) of jets, missing transverse momentum and no isolated electrons or muons. This analysis uses 20.3/fb of pp collision data at sqrt(s)=8 TeV collected by the ATLAS experiment at the Large Hadron Collider. The sensitivity of the search is enhanced by considering the number of b-tagged jets and the scalar sum of masses of large-radius jets in an event. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of various simplified supersymmetry-inspired models where gluinos are pair produced, as well as a mSUGRA/CMSSM model..
436. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Dynamics of isolated-photon plus jet production in pp collisions at√s = 7 TeV with the ATLAS detector, Nucl. Phys. B, 10.1016/j.nuclphysb.2013.07.025, 875, 483-535, 2013.10, The dynamics of isolated-photon plus jet production in pp collisions at a centre-of-mass energy of 7 TeV has been studied with the ATLAS detector at the LHC using an integrated luminosity of 37 pb-1. Measurements of isolated-photon plus jet bin-averaged cross sections are presented as functions of photon transverse energy, jet transverse momentum and jet rapidity. In addition, the bin-averaged cross sections as functions of the difference between the azimuthal angles of the photon and the jet, the photon--jet invariant mass and the scattering angle in the photon--jet centre-of-mass frame have been measured. Next-to-leading-order QCD calculations are compared to the measurements and provide a good description of the data, except for the case of the azimuthal opening angle..
437. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the differential cross section of B+ meson production in pp collisions at √s = 7 TeV at ATLAS, JHEP, 10.1007/JHEP10(2013)042, 2013, 10, 042, 2013.10, The production cross-section of B+ mesons is measured as a function of transverse momentum pT and rapidity y in proton--proton collisions at center-of-mass energy sqrt(s) = 7 TeV, using 2.4 fb-1 of data recorded with the ATLAS detector at the Large Hadron Collider. The differential production cross-sections, determined in the range 9
438. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the azimuthal angle dependence of inclusive jet yields in Pb+Pb collisions at √sNN=2.76 TeV with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.111.152301, 111, 152301, 2013.10, Measurements of the variation of inclusive jet suppression as a function of relative azimuthal angle, Delta phi, with respect to the elliptic event plane provide insight into the path-length dependence of jet quenching. ATLAS has measured the Delta phi dependence of jet yields in 0.14 nb^-1 of sqrt(s(NN))= 2.76 TeV Pb+Pb collisions at the LHC for jet transverse momenta p_T > 45 GeV in different collision centrality bins using an underlying event subtraction procedure that accounts for elliptic flow. The variation of the jet yield with Delta phi was characterized by the parameter, v_2^jet, and the ratio of out-of-plane (Delta phi ~ pi/2) to in-plane (Delta phi ~ 0) yields. Non-zero v_2^jet values were measured in all centrality bins for p_T < 160 GeV. The jet yields are observed to vary by as much as 20% between in-plane and out-of-plane directions..
439. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the high-mass Drell-Yan differential cross-section in pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2013.07.049, 725, 223-242, 2013.10, This Letter reports a measurement of the high-mass Drell-Yan differential cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC. Based on an integrated luminosity of 4.9 /fb, the differential cross-section in the Z/gamma* to e+e- channel is measured with the ATLAS detector as a function of the invariant mass, Mee, in the range 116 < Mee < 1500 GeV, for a fiducial region in which both the electron and the positron have transverse momentum pT > 25 GeV and pseudorapidity eta < 2.5. A comparison is made to various event generators and to the predictions of perturbative QCD calculations at next-to-next-to-leading order..
440. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Microscopic Black Holes in a Like-sign Dimuon Final State using large Track Multiplicity with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.88.072001, 88, 072001, 2013.10, A search is presented for microscopic black holes in a like-sign dimuon final state in proton--proton collisions at sqrt(s)= 8 TeV. The data were collected with the ATLAS detector at the Large Hadron Collider in 2012 and correspond to an integrated luminosity of 20.3 fb-1. Using a high track multiplicity requirement, 0.6 +- 0.2 background events from Standard Model processes are predicted and none observed. This result is interpreted in the context of low-scale gravity models and 95% CL lower limits on microscopic black hole masses are set for different model assumptions..
441. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for direct third-generation squark pair production in final states with missing transverse momentum and two b-jets in √s =8 TeV pp collisions with the ATLAS detector, JHEP, 10.1007/JHEP10(2013)189, 2013, 10, 189, 2013.10, The results of a search for pair production of supersymmetric partners of the Standard Model third-generation quarks are reported. This search uses 20.1 fb-1 of pp collisions at sqrt{s}=8 TeV collected by the ATLAS experiment at the Large Hadron Collider. The lightest bottom and top squarks (b1 and t1 respectively) are searched for in a final state with large missing transverse momentum and two jets identified as originating from b-quarks. No excess of events above the expected level of Standard Model background is found. The results are used to set upper limits on the visible cross section for processes beyond the Standard Model. Exclusion limits at the 95% confidence level on the masses of the third-generation squarks are derived in phenomenological supersymmetric R-parity-conserving models in which either the bottom or the top squark is the lightest squark. The b1 is assumed to decay via b1->b chi0 and the t via t1->b chipm, with undetectable products of the subsequent decay of the chipm due to the small mass splitting between the chipm and the chi0..
442. C. Adloff, K. Kawagoe et al. (The CALICE collaboration), Track segments in hadronic showers in a highly granular scintillator-steel hadron calorimeter, JOURNAL OF INSTRUMENTATION, 10.1088/1748-0221/8/09/P09001, 8, 2013.09.
443. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for excited electrons and muons with proton-proton collisions at √s =8 TeV with the ATLAS detector, New J. Phys., 10.1088/1367-2630/15/9/093011, 15, 93011, 2013.09, The ATLAS detector at the LHC is used to search for excited electrons and excited muons in the channel pp -> ll* -> llgamma, assuming that excited leptons are produced via contact interactions. The analysis is based on 13 fb-1 of pp collisions at a centre-of-mass energy of 8 TeV. No evidence for excited leptons is found, and a limit is set at the 95% credibility level on the cross section times branching ratio as a function of the excited-lepton mass m_l*. For m_l* > 0.8 TeV, the respective upper limits on sigma*B(l* -> lgamma) are 0.75 fb and 0.90 fb for the e* and mu* searches. Limits on sigma*B are converted into lower bounds on the compositeness scale Lambda. In the special case where Lambda = m_l*, excited-electron and excited-muon masses below 2.2 TeV are excluded..
444. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Performance of jet substructure techniques for large-R jets in proton-proton collisions at √s = 7 TeV using the ATLAS detector, JHEP, 10.1007/JHEP09(2013)076, 2013, 09, 076, 2013.09, This paper presents the application of a variety of techniques to study jet substructure. The performance of various modified jet algorithms, or jet grooming techniques, for several jet types and event topologies is investigated for jets with transverse momentum larger than 300 GeV. Properties of jets subjected to the mass-drop filtering, trimming, and pruning algorithms are found to have reduced sensitivity to multiple proton-proton interactions, are more stable at high luminosity and improve the physics potential of searches for heavy boosted objects. Studies of the expected discrimination power of jet mass and jet substructure observables in searches for new physics are also presented. Event samples enriched in boosted W and Z bosons and top-quark pairs are used to study both the individual jet invariant mass scales and the efficacy of algorithms to tag boosted hadronic objects. The analyses presented use the full 2011 ATLAS dataset, corresponding to an integrated luminosity of 4.7 +/- 0.1 /fb from proton-proton collisions produced by the Large Hadron Collider at a center-of-mass energy of sqrt(s) = 7 TeV..
445. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Improved luminosity determination in pp collisions at √s = 7 TeV using the ATLAS detector at the LHC, Eur. Phys. J. C, 10.1140/epjc/s10052-013-2518-3, 73, 2518, 2013.08, The luminosity calibration for the ATLAS detector at the LHC during pp collisions at sqrt(s) = 7 TeV in 2010 and 2011 is presented. Evaluation of the luminosity scale is performed using several luminosity-sensitive detectors, and comparisons are made of the long-term stability and accuracy of this calibration applied to the pp collisions at sqrt(s) = 7 TeV. A luminosity uncertainty of Delta L/L = +/- 3.5% is obtained for the 47 pb-1 of data delivered to ATLAS in 2010, and an uncertainty of Delta L/L = +/- 1.8% is obtained for the 5.5 fb-1 delivered in 2011..
446. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of multi-particle azimuthal correlations in proton-lead collisions at √sNN = 5.02 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2013.06.057, 725, 60-78, 2013.08, In order to study further the long-range correlations ("ridge") observed recently in p+Pb collisions at sqrt(s_NN) =5.02 TeV, the second-order azimuthal anisotropy parameter of charged particles, v_2, has been measured with the cumulant method using the ATLAS detector at the LHC. In a data sample corresponding to an integrated luminosity of approximately 1 microb^(-1), the parameter v_2 has been obtained using two- and four-particle cumulants over the pseudorapidity range |eta|<2.5. The results are presented as a function of transverse momentum and the event activity, defined in terms of the transverse energy summed over 3.1
447. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the inclusive jet cross section in pp collisions at √s = 2.76 TeV and comparison to the inclusive jet cross section at √s = 7 TeV using the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-013-2509-4, 73, 2509, 2013.08, The inclusive jet cross-section has been measured in proton-proton collisions at sqrt(s)=2.76 TeV in a dataset corresponding to an integrated luminosity of 0.20pb-1 collected with the ATLAS detector at the Large Hadron Collider in 2011. Jets are identified using the anti-kt algorithm with two radius parameters of 0.4 and 0.6. The inclusive jet double-differential cross-section is presented as a function of the jet transverse momentum pT and jet rapidity y, covering a range of 20 <= pT < 430 GeV and |y| < 4.4. The ratio of the cross-section to the inclusive jet cross-section measurement at sqrt(s)=7 TeV, published by the ATLAS Collaboration, is calculated as a function of both transverse momentum and the dimensionless quantity xT = 2 pT / sqrt(s), in bins of jet rapidity. The systematic uncertainties on the ratios are significantly reduced due to the cancellation of correlated uncertainties in the two measurements. Results are compared to the prediction from next-to-leading order perturbative QCD calculations corrected for non-perturbative effects, and next-to-leading order Monte Carlo simulation. Furthermore, the ATLAS jet cross-section measurements at sqrt(s)=2.76 TeV and sqrt(s)=7 TeV are analysed within a framework of next-to-leading order perturbative QCD calculations to determine parton distribution functions of the proton, taking into account the correlations between the measurements..
448. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of charged-particle event shape variables in √s = 7 TeV proton-proton interactions with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.88.032004, 88, 032004, 2013.08, The measurement of charged-particle event shape variables is presented in inclusive inelastic pp collisions at a center-of-mass energy of 7 TeV using the ATLAS detector at the LHC. The observables studied are the transverse thrust, thrust minor and transverse sphericity, each defined using the final-state charged particles' momentum components perpendicular to the beam direction. Events with at least six charged particles are selected by a minimum-bias trigger. In addition to the differential distributions, the evolution of each event shape variable as a function of the leading charged particle transverse momentum, charged particle multiplicity and summed transverse momentum is presented. Predictions from several Monte Carlo models show significant deviations from data. .
449. C. Adloff, K. Kawagoe et al. (The CALICE collaboration), Validation of GEANT4 Monte Carlo models with a highly granular scintillator-steel hadron calorimeter, JOURNAL OF INSTRUMENTATION, 10.1088/1748-0221/8/07/P07005, 8, 2013.07.
450. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A search for ttbar resonances in the lepton plus jets final state with ATLAS using 4.7 fb-1 of pp collisions at √s = 7 TeV, Phys. Rev. D, 10.1103/PhysRevD.88.012004, 88, 012004, 2013.07, A search for new particles that decay into top quark pairs (ttbar) is performed with the ATLAS experiment at the LHC using an integrated luminosity of 4.7 fb^-1 of proton-proton (pp) collision data collected at a center-of-mass energy sqrt(s)=7 TeV. In the ttbar --> WbWb decay, the lepton plus jets final state is used, where one W boson decays leptonically and the other hadronically. The ttbar system is reconstructed using both small-radius and large-radius jets, the latter being supplemented by a jet substructure analysis. A search for local excesses in the number of data events compared to the Standard Model expectation in the ttbar invariant mass spectrum is performed. No evidence for a ttbar resonance is found and 95% credibility-level limits on the production rate are determined for massive states predicted in two benchmark models. The upper limits on the cross section times branching ratio of a narrow Z' resonance range from 5.1 pb for a boson mass of 0.5 TeV to 0.03 pb for a mass of 3 TeV. A narrow leptophobic topcolor Z' resonance with a mass below 1.74 TeV is excluded. Limits are also derived for a broad color-octet resonance with Gamma/m = 15.3%. A Kaluza-Klein excitation of the gluon in a Randall-Sundrum model is excluded for masses below 2.07 TeV..
451. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Triggers for Displaced Decays of Long-lived Neutral Particles in the ATLAS Detector, JINST, 10.1088/1748-0221/8/07/P07015, 8, 07, P07015, 2013.07, A set of three dedicated triggers designed to detect long-lived neutral particles decaying throughout the ATLAS detector to a pair of hadronic jets is described. The efficiencies of the triggers for selecting displaced decays as a function of the decay position are presented for simulated events. The effect of pile-up interactions on the trigger efficiencies and the dependence of the trigger rate on instantaneous luminosity during the 2012 data-taking period at the LHC are discussed..
452. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Characterisation and mitigation of beam-induced backgrounds observed in the ATLAS detector during the 2011 proton-proton run, JINST, 10.1088/1748-0221/8/07/P07004, 8, 07, P07004, 2013.07, This paper presents a summary of beam-induced backgrounds observed in the ATLAS detector and discusses methods to tag and remove background contaminated events in data. Trigger-rate based monitoring of beam-related backgrounds is presented. The correlations of backgrounds with machine conditions, such as residual pressure in the beam-pipe, are discussed. Results from dedicated beam-background simulations are shown, and their qualitative agreement with data is evaluated. Data taken during the passage of unpaired, i.e. non-colliding, proton bunches is used to obtain background-enriched data samples. These are used to identify characteristic features of beam-induced backgrounds, which then are exploited to develop dedicated background tagging tools. These tools, based on observables in the Pixel detector, the muon spectrometer and the calorimeters, are described in detail and their efficiencies are evaluated. Finally an example of an application of these techniques to a monojet analysis is given, which demonstrates the importance of such event cleaning techniques for some new physics searches..
453. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the production cross section of jets in association with a Z boson in pp collisions at √s = 7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP07(2013)032, 2013, 07, 032, 2013.07, Measurements of the production of jets of particles in association with a Z boson in pp collisions at sqrt(s) = 7 TeV are presented, using data corresponding to an integrated luminosity of 4.6/fb collected by the ATLAS experiment at the Large Hadron Collider. Inclusive and differential jet cross sections in Z events, with Z decaying into electron or muon pairs, are measured for jets with transverse momentum pT > 30 GeV and rapidity |y| < 4.4. The results are compared to next-to-leading-order perturbative QCD calculations, and to predictions from different Monte Carlo generators based on leading-order and next-to-leading-order matrix elements supplemented by parton showers..
454. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for non-pointing photons in the diphoton and ETmiss final state in √s = 7 TeV pp collisions using the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.88.012001, 88, 012001, 2013.07, A search has been performed for photons originating in the decay of a neutral long-lived particle, exploiting the capabilities of the ATLAS electromagnetic calorimeter to make precise measurements of the flight direction of photons, as well as the calorimeter's excellent time resolution. The search has been made in the diphoton plus missing transverse energy final state, using the full data sample of 4.8/fb of 7 TeV proton-proton collisions collected in 2011 with the ATLAS detector at the LHC. No excess is observed above the background expected from Standard Model processes. The results are used to set exclusion limits in the context of Gauge Mediated Supersymmetry Breaking models, with the lightest neutralino being the next-to-lightest supersymmetric particle and decaying with a lifetime in excess of 0.25 ns into a photon and a gravitino..
455. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a heavy narrow resonance decaying to e-mu, e-tau or mu-tau with the ATLAS detector in √s =7 TeV pp collisions at the LHC, Phys. Lett. B, 10.1016/j.physletb.2013.04.035, 723, 15-32, 2013.06, This letter presents the results of a search for a heavy particle decaying into an e mu, e tau, or mu tau final state in pp collisions at sqrt(s) = 7 TeV. The data were recorded with the ATLAS detector at the LHC during 2011 and correspond to an integrated luminosity of 4.6/fb. No significant excess above the Standard Model expectation is observed, and exclusions at 95% confidence level are placed on the cross section times branching ratio for the production of an R-parity-violating supersymmetric tau sneutrino. These results considerably extend constraints from Tevatron experiments..
456. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of Wgamma and Zgamma production in pp collisions at √s = 7 TeV with the ATLAS detector at the LHC, Phys. Rev. D, 10.1103/PhysRevD.87.112003, 87, 112003, 2013.06, The integrated and differential fiducial cross sections for the production of a W or Z boson in association with a high-energy photon are measured using pp collisions at sqrt{s} = 7 TeV. The analyses use a data sample with an integrated luminosity of 4.6 fb^{-1} collected by the ATLAS detector during the 2011 LHC data-taking period. Events are selected using leptonic decays of the W and Z bosons (W(e nu,mu nu) and Z(e+ e-, mu+ mu-, nu nubar)) with the requirement of an associated isolated photon. The data are used to test the electroweak sector of the Standard Model and search for evidence for new phenomena. The measurements are used to probe the anomalous WWgamma, ZZgamma and Zgammagamma triple-gauge-boson couplings and to search for the production of vector resonances decaying to Zgamma and Wgamma. No deviations from Standard Model predictions are observed and limits are placed on anomalous triple-gauge-boson couplings and on the production of new vector meson resonances..
457. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the cross-section for W boson production in association with b-jets in pp collisions at √s = 7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP06(2013)084, 2013, 06, 084, 2013.06, This paper reports a measurement of the W+b-jets production cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC. These results are based on data corresponding to an integrated luminosity of 4.6 fb-1, collected with the ATLAS detector. Cross-sections are presented as a function of jet multiplicity and of the transverse momentum of the leading b-jet for both the muon and electron decay modes of the W boson. The W+b-jets cross-section, corrected for all known detector effects, is quoted in a limited kinematic range, using jets reconstructed with the anti-k_t clustering algorithm with transverse momentum above 25 GeV and rapidity within +/- 2.1. Combining the muon and electron channels, the fiducial cross-section for W+b-jets is measured to be 7.1 +/- 0.5 (stat) +/- 1.4 (syst) pb, consistent with next-to-leading order QCD calculations within 1.5 standard deviations..
458. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a light charged Higgs boson in the decay channel H+ → csbar in ttbar events using pp collisions at √s = 7 TeV with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-013-2465-z, 73, 2465, 2013.06, A search for a charged Higgs boson (H+) in ttbar decays is presented, where one of the top quarks decays via t->H+b, followed by H+->two jets (csbar). The other top quark decays to Wb, where the W boson then decays into a lepton (e/mu) and a neutrino. The data were recorded in pp collisions at sqrt(s) = 7TeV by the ATLAS detector at the LHC in 2011, and correspond to an integrated luminosity of 4.7 fb-1. With no observation of a signal, 95% confidence level (CL) upper limits are set on the decay branching ratio of top quarks to charged Higgs bosons varying between 5% and 1% for H+ masses between 90 GeV and 150 GeV, assuming Br(H+->csbar)=100%..
459. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for third generation scalar leptoquarks in pp collisions at √s = 7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP06(2013)033, 2013, 06, 033, 2013.06, A search for pair-produced third generation scalar leptoquarks is presented, using proton-proton collisions at sqrt(s)= 7 TeV at the LHC. The data were recorded with the ATLAS detector and correspond to an integrated luminosity of 4.7 fb-1. Each leptoquark is assumed to decay to a tau lepton and a b-quark with a branching fraction equal to 100%. No statistically significant excess above the Standard Model expectation is observed. Third generation leptoquarks are therefore excluded at 95% confidence level for masses less than 534 GeV..
460. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for heavy resonance decaying to WW or WZ in the lvjj and lvJ (boosted) final states, Phys. Rev. D, 10.1103/PhysRevD.87.112006, 87, 112006, 2013.06, A search for resonant diboson production using a data sample corresponding to 4.7 fb-1 of integrated luminosity collected by the ATLAS experiment at the Large Hadron Collider in pp collisions at 7 TeV is presented. The search for a narrow resonance in the WW or WZ mass distribution is conducted in a final state with an electron or a muon, missing transverse momentum and at least two jets. No significant excess is observed and limits are set using three benchmark models: WW resonance masses below 940 GeV and 710 GeV are excluded at 95% confidence level for spin-2 Randall-Sundrum and bulk Randall-Sundrum gravitons, respectively; WZ resonance masses below 950 GeV are excluded at 95% confidence level for a spin-1 Extended Gauge Model W' boson..
461. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of W+W- production in pp collisions at √s = 7 TeV with the ATLAS detector and limits on anomalous WWZ and WWgamma couplings, Phys. Rev. D, 10.1103/PhysRevD.87.112001, 87, 112001, 2013.06, This paper presents a measurement of the W^+W^- production cross section in pp collisions at sqrt{s}=7 TeV. The leptonic decay channels are analyzed using data corresponding to an integrated 4.6 fb-1 collected with the ATLAS detector at the Large Hadron Collider. The W^+W^- production cross section sigma(pp -> W^+W^-+X) is measured to be 51.9 +- 2.0 (stat) +- 3.9 (syst) +- 2.0 (lumi) pb, compatible with the Standard Model prediction of 44.7 +2.1 -1.9 pb. A measurement of the normalized fiducial cross section as a function of the leading lepton transverse momentum is also presented. The reconstructed transverse momentum distribution of the leading lepton is used to extract limits on anomalous WWZ and WWgamma couplings..
462. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Observation of associated near- and away-side long-range pseudorapidity correlations in √sNN =5.02 TeV proton-lead collisions at the LHC with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.110.182302, 110, 182302, 2013.05, Two-particle correlations in relative azimuthal angle (Delta-phi) and pseudorapidity (Delta-eta) are measured in sqrt(s_NN) = 5.02 TeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1 mub^-1 of data as a function of p_T and the transverse energy (SumE_T) summed over 3.1 < eta < 4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Delta-eta|<5) near-side (Delta-phi ~ 0) correlation that grows rapidly with increasing SumE_T. A long-range away-side (Delta-phi ~ pi) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small SumE_T, is found to match the near-side correlation in magnitude, shape (in Delta-eta and Delta-phi) and SumE_T dependence. The resultant Delta-phi correlation is approximately symmetric about pi/2, and is consistent with a cos(2Delta-phi) modulation for all SumE_T ranges and particle p_T. The amplitude of this modulation is comparable in magnitude and p_T dependence to similar modulations observed in heavy-ion collisions, suggestive of final-state collective effects in high multiplicity events..
463. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for long-lived, multi-charged particles in pp collisions at √s = 7 TeV using the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2013.04.036, 722, 305-323, 2013.05, A search for highly ionising, penetrating particles with electric charges from |q| = 2e to 6e is performed using the ATLAS detector at the CERN Large Hadron Collider. Proton-proton collision data taken at sqrt(s)=7 TeV during the 2011 running period, corresponding to an integrated luminosity of 4.4 fb^-1, are analysed. No signal candidates are observed, and 95% confidence level cross-section upper limits are interpreted as mass-exclusion lower limits for a simplified Drell--Yan production model. In this model, masses are excluded from 50 GeV up to 430, 480, 490, 470 and 420 GeV for charges 2e, 3e, 4e, 5e and 6e, respectively..
464. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of kt splitting scales in W→lnu events at √s = 7 TeV with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-013-2432-8, 73, 2432, 2013.05, A measurement of splitting scales, as defined by the kT clustering algorithm, is presented for final states containing a W boson produced in proton--proton collisions at a centre-of-mass energy of 7 TeV. The measurement is based on the full 2010 data sample corresponding to an integrated luminosity of 36 pb-1 which was collected using the ATLAS detector at the CERN Large Hadron Collider. Cluster splitting scales are measured in events containing W bosons decaying to electrons or muons. The measurement comprises the four hardest splitting scales in a kT cluster sequence of the hadronic activity accompanying the W boson, and ratios of these splitting scales. Backgrounds such as multi-jet and top-quark-pair production are subtracted and the results are corrected for detector effects. Predictions from various Monte Carlo event generators at particle level are compared to the data. Overall, reasonable agreement is found with all generators, but larger deviations between the predictions and the data are evident in the soft regions of the splitting scales..
465. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for single b*-quark production with the ATLAS detector at √s = 7 TeV, Phys. Lett. B, 10.1016/j.physletb.2013.03.016, 721, 171-189, 2013.04, The results of a search for an excited bottom-quark b* in pp collisions at sqrt(s)=7 TeV, using 4.7/fb of data collected by the ATLAS detector at the LHC are presented. In the model studied, a single b*-quark is produced through a chromomagnetic interaction and subsequently decays to a W boson and a top-quark. The search is performed in the dilepton and lepton+jets final states, which are combined to set limits on b*-quark couplings for a range of b*-quark masses. For a benchmark with unit size chromomagnetic and Standard Model-like electroweak b* couplings, b*-quarks with masses less than 870 GeV are excluded at the 95% credibility level..
466. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for WH production with a light Higgs boson decaying to prompt electron-jets in proton-proton collisions at √s = 7 TeV with the ATLAS detector, New J. Phys., 10.1088/1367-2630/15/4/043009, 15, 043009, 2013.04, A search is performed for WH production with a light Higgs boson decaying to hidden-sector particles resulting in clusters of collimated electrons, known as electron-jets. The search is performed with 2.04 fb-1 of data collected in 2011 with the ATLAS detector at the LHC in proton-proton collisions at sqrt(s)=7 TeV. One event satisfying the signal selection criteria is observed, which is consistent with the expected background rate. Limits on the product of the WH production cross section and the branching ratio of a Higgs boson decaying to prompt electron-jets are calculated as a function of a Higgs boson mass in the range from 100 GeV to 140 GeV..
467. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for extra dimensions in diphoton events using proton-proton collisions recorded at √s =7 TeV with the ATLAS detector at the LHC, New J. Phys., 10.1088/1367-2630/15/4/043007, 15, 043007, 2013.04, The large difference between the Planck scale and the electroweak scale, known as the hierarchy problem, is addressed in certain models through the postulate of extra spatial dimensions. A search for evidence of extra spatial dimensions in the diphoton channel has been performed using the full set of proton-proton collisions at sqrt(s) = 7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. This dataset corresponds to an integrated luminosity of 4.9 fb. The diphoton invariant mass spectrum is observed to be in good agreement with the Standard Model expectation. In the context of the model proposed by Arkani-Hamed, Dimopoulos and Dvali, 95% confidence level lower limits of between 2.52 TeV and 3.92 TeV are set on the ultraviolet cutoff scale Ms depending on the number of extra dimensions and the theoretical formalism used. In the context of the Randall--Sundrum model, a lower limit of 2.06 (1.00) TeV at 95% confidence level is set on the mass of the lightest graviton for couplings of k/Mpl = 0.1 (0.01). Combining with the ATLAS dilepton searches based on the 2011 data, the 95% confidence level lower limit on the Randall--Sundrum graviton mass is further tightened to 2.23 (1.03) TeV for k/Mpl = 0.1 (0.01)..
468. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for dark matter and large extra dimensions in events with a jet and missing transverse momentum with the ATLAS detector, JHEP, 10.1007/JHEP04(2013)075, 2013, 04, 075, 2013.04, A search for new phenomena in events with a high-energy jet and large missing transverse momentum is performed using data from proton-proton collisions at sqrt(s)=7 TeV with the ATLAS experiment at the Large Hadron Collider. Four kinematic regions are explored using a dataset corresponding to an integrated luminosity of 4.7 inverse femtobarn. No excess of events beyond expectations from Standard Model processes is observed, and limits are set on large extra dimensions and the pair production of dark matter particles..
469. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Displaced Muonic Lepton Jets from light Higgs boson decay in proton-proton collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2013.02.058, 721, 32-50, 2013.04, A search is performed for collimated muon pairs displaced from the primary vertex produced in the decay of long-lived neutral particles in proton-proton collisions at sqrt(s) = 7 TeV centre-of-mass energy, with the ATLAS detector at the LHC. In a 1.9 fb-1 event sample collected during 2011, the observed data are consistent with the Standard Model background expectations. Limits on the product of the production cross section and the branching ratio of a Higgs boson decaying to hidden-sector neutral long-lived particles are derived as a function of the particles' mean lifetime..
470. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for light top squark pair production in final states with leptons and b-jets with the ATLAS detector in √s = 7 TeV proton-proton collisions, Phys. Lett. B, 10.1016/j.physletb.2013.01.049, 720, 13-31, 2013.03, The results of a search for pair production of light top squarks are presented, using 4.7 fb^-1 of sqrt(s) = 7 TeV proton-proton collisions collected with the ATLAS detector at the Large Hadron Collider. This search targets top squarks with masses similar to, or lighter than, the top quark mass. Final states containing exclusively one or two leptons (e, mu), large missing transverse momentum, light-jets and b-jets are used to reconstruct the top squark pair system. Global mass scale variables are used to separate the signal from a large ttbar background. No excess over the Standard Model expectations is found. The results are interpreted in the framework of the Minimal Supersymmetric Standard Model, assuming the top squark decays exclusively to a chargino and a b-quark. Light top squarks with masses between 123-167 GeV are excluded for neutralino masses around 55 GeV..
471. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Jet energy resolution in proton-proton collisions at √s = 7 TeV recorded in 2010 with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-013-2306-0, 73, 2306, 2013.03, The measurement of the jet energy resolution is presented using data recorded with the ATLAS detector in proton-proton collisions at sqrt(s) = 7 TeV. The sample corresponds to an integrated luminosity of 35 pb-1. Jets are reconstructed from energy deposits measured by the calorimeters and calibrated using different jet calibration schemes. The jet energy resolution is measured with two different in situ methods which are found to be in agreement within uncertainties. The total uncertainties on these measurements range from 20% to 10% for jets within |y|<2.8 and with transverse momenta increasing from 30 GeV to 500 GeV. Overall, the Monte Carlo simulation of the jet energy resolution agrees with the data within 10%..
472. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Searches for heavy long-lived sleptons and R-hadrons with the ATLAS detector in pp collisions at √s = 7 TeV, Phys. Lett. B, 10.1016/j.physletb.2013.02.015, 720, 277-308, 2013.03, A search for long-lived particles is performed using a data sample of 4.7 fb-1 from proton-proton collisions at a centre-of-mass energy sqrt(s) = 7 TeV collected by the ATLAS detector at the LHC. No excess is observed above the estimated background and lower limits, at 95% confidence level, are set on the mass of the long-lived particles in different scenarios, based on their possible interactions in the inner detector, the calorimeters and the muon spectrometer. Long-lived staus in gauge-mediated SUSY-breaking models are excluded up to a mass of 300 GeV for tan beta = 5-20. Directly produced long-lived sleptons are excluded up to a mass of 278 GeV. R-hadrons, composites of gluino (stop, sbottom) and light quarks, are excluded up to a mass of 985 GeV (683 GeV, 612 GeV) when using a generic interaction model. Additionally two sets of limits on R-hadrons are obtained that are less sensitive to the interaction model for R-hadrons. One set of limits is obtained using only the inner detector and calorimeter observables, and a second set of limits is obtained based on the inner detector alone..
473. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of ZZ production in pp collisions at √s = 7 TeV and limits on anomalous ZZZ and ZZgamma couplings with the ATLAS detector, JHEP, 10.1007/JHEP03(2013)128, 2013, 03, 128, 2013.03, A measurement of the ZZ production cross section in proton-proton collisions at sqrt(s) = 7 TeV using data recorded by the ATLAS experiment at the Large Hadron Collider is presented. In a data sample corresponding to an integrated luminosity of 4.6 fb-1 collected in 2011, events are selected that are consistent either with two Z bosons decaying to electrons or muons or with one Z boson decaying to electrons or muons and a second Z boson decaying to neutrinos. The ZZ*->llll and ZZ->llnunu cross sections are measured in restricted phase-space regions. These results are then used to derive the total cross section for ZZ events produced with both Z bosons in the mass range 66 to 116 GeV, sigmaZZtot = 6.7 +-0.7 +0.4-0.3 +-0.3 pb, which is consistent with the Standard Model prediction of 5.89+0.22-0.18 pb calculated at next-to-leading order in QCD. The normalized differential cross sections in bins of various kinematic variables are presented. Finally, the differential event yield as a function of the transverse momentum of the leading Z boson is used to set limits on anomalous neutral triple gauge boson couplings in ZZ production..
474. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena in events with three charged leptons at √s = 7 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.87.052002, 87, 052002, 2013.03, A generic search for anomalous production of events with at least three charged leptons is presented. The search uses a pp-collision data sample at a center-of-mass energy of 7 TeV corresponding to 4.6 inverse femtobarns of integrated luminosity collected in 2011 by the ATLAS detector at the CERN Large Hadron Collider. Events are required to contain at least two electrons or muons, while the third lepton may either be an additional electron or muon, or a hadronically decaying tau lepton. Events are categorized by the presence or absence of a reconstructed tau-lepton or Z-boson candidate decaying to leptons. No significant excess above backgrounds expected from Standard Model processes is observed. Results are presented as upper limits on event yields from non-Standard-Model processes producing at least three prompt, isolated leptons, given as functions of lower bounds on several kinematic variables. Fiducial efficiencies for model testing are also provided. The use of the results is illustrated by setting upper limits on the production of doubly-charged Higgs bosons decaying to same-sign lepton pairs..
475. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of angular correlations in Drell-Yan lepton pairs to probe Z/gamma* boson transverse momentum at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2013.01.054, 720, 32-51, 2013.03, A measurement of angular correlations in Drell-Yan lepton pairs via the phistar observable is presented. This variable probes the same physics as the Z/gamma* boson transverse momentum with a better experimental resolution. The Z/gamma*->e+e- and Z/gamma*->mu+mu- decays produced in proton--proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV are used. The data were collected with the ATLAS detector at the LHC and correspond to an integrated luminosity of 4.6 fb-1. Normalised differential cross sections as a function of phistar are measured separately for electron and muon decay channels. These channels are then combined for improved accuracy. The cross section is also measured double differentially as a function of phistar for three independent bins of the Z boson rapidity. The results are compared to QCD calculations and to predictions from different Monte Carlo event generators. The data are reasonably well described, in all measured Z boson rapidity regions, by resummed QCD predictions combined with fixed-order perturbative QCD calculations. Some of the Monte Carlo event generators are also able to describe the data. The measurement precision is typically better by one order of magnitude than present theoretical uncertainties..
476. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the tt production cross section in the tau+jets channel using the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-013-2328-7, 73, 2328, 2013.03, A measurement of the top quark pair production cross section in the final state with a hadronically decaying tau lepton and jets is presented. The analysis is based on proton-proton collision data recorded by the ATLAS experiment at the LHC, with a centre-of-mass energy of 7 TeV. The data sample corresponds to an integrated luminosity of 1.67 inverse femtobarns. The cross section is measured to be 194 +/- 18 (stat.) +/- 46 (syst.) pb and is in agreement with other measurements and with the Standard Model prediction..
477. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of Υ production in 7 TeV pp collisions at ATLAS, Phys. Rev. D, 10.1103/PhysRevD.87.052004, 87, 052004, 2013.03, Using 1.8 fb-1 of pp collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the Large Hadron Collider, we present measurements of the production cross sections of Upsilon(1S,2S,3S) mesons. Upsilon mesons are reconstructed using the di-muon decay mode. Total production cross sections for p_T<70 GeV and in the rapidity interval |Upsilon|<2.25 are measured to be 8.01+-0.02+-0.36+-0.31 nb, 2.05+-0.01+-0.12+-0.08 nb, 0.92+-0.01+-0.07+-0.04 nb respectively, with uncertainties separated into statistical, systematic, and luminosity measurement effects. In addition, differential cross section times di-muon branching fractions for Upsilon(1S), Upsilon(2S), and Upsilon(3S) as a function of Upsilon transverse momentum p_T and rapidity are presented. These cross sections are obtained assuming unpolarized production. If the production polarization is fully transverse or longitudinal with no azimuthal dependence in the helicity frame the cross section may vary by approximately +-20%. If a non-trivial azimuthal dependence is considered, integrated cross sections may be significantly enhanced by a factor of two or more. We compare our results to several theoretical models of Upsilon meson production, finding that none provide an accurate description of our data over the full range of Upsilon transverse momenta accessible with this dataset..
478. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for charged Higgs bosons through the violation of lepton universality in ttbar events using pp collision data at √s = 7 TeV with the ATLAS, JHEP, 10.1007/JHEP03(2013)076, 2013, 03, 076, 2013.03, In several extensions of the Standard Model, the top quark can decay into a bottom quark and a light charged Higgs boson H+, t to bH+, in addition to the Standard Model decay t to bW. Since W bosons decay to the three lepton generations equally, while H+ may predominantly decay into tau+nu, charged Higgs bosons can be searched for using the violation of lepton universality in top quark decays. The analysis in this paper is based on 4.6/fb of proton-proton collision data at sqrt(s) = 7 TeV collected by the ATLAS experiment at the Large Hadron Collider. Signatures containing leptons (e or mu) and/or a hadronically decaying tau (tau_had) are used. Event yield ratios between e+tau_had and e+mu, as well as between mu+tau_had and mu+e, final states are measured in the data and compared to predictions from simulations. This ratio-based method reduces the impact of systematic uncertainties in the analysis. No significant deviation from the Standard Model predictions is observed. With the assumption that the branching fraction B(H+ to tau+nu) is 100%, upper limits in the range 3.2%-4.4% can be placed on the branching fraction B(t to bH+) for charged Higgs boson masses m(H+) in the range 90-140 GeV. After combination with results from a search for charged Higgs bosons in ttbar decays using the tau_had+jets final state, upper limits on B(t to bH+) can be set in the range 0.8%-3.4%, for m(H+) in the range 90-160 GeV..
479. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Multi-channel search for squarks and gluinos in √s = 7 TeV pp collisions with the ATLAS detector at the LHC, Eur. Phys. J. C, 10.1140/epjc/s10052-013-2362-5, 73, 2362, 2013.03, A search for supersymmetric particles in final states with zero, one, and two leptons, with and without jets identified as originating from b-quarks, in 4.7 fb-1 of sqrt(s)=7 TeV pp collisions produced by the Large Hadron Collider and recorded by the ATLAS detector is presented. The search uses a set of variables carrying information on the event kinematics transverse and parallel to the beam line that are sensitive to several topologies expected in supersymmetry. Mutually exclusive final states are defined, allowing a combination of all channels to increase the search sensitivity. No deviation from the Standard Model expectation is observed. Upper limits at 95% confidence level on fiducial cross-sections for the production of new particles are extracted. Results are interpreted in the context of the constrained minimal supersymmetric extension to the Standard Model and in supersymmetry-inspired models with diverse, high-multiplicity final states..
480. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of hard double-parton interactions in W (→ lnu) + 2 jet events at √s = 7 TeV with the ATLAS detector, New J. Phys., 10.1088/1367-2630/15/3/033038, 15, 033038, 2013.03, The production of W bosons in association with two jets in proton-proton collisions at a centre-of-mass energy of sqrt(s)=7 TeV has been analysed for the presence of double-parton interactions using data corresponding to an integrated luminosity of 36/pb, collected with the ATLAS detector at the LHC. The fraction of events arising from double-parton interactions, fDP(D) has been measured through the momentum balance between the two jets and amounts to fDP(D) = 0.08 +- 0.01 (stat.) +- 0.02 (sys) for jets with transverse momentum PT > 20 GeV and rapidity |y|<2.8. This corresponds to a measurement of the effective area parameter for hard double-parton interactions of sigma_eff = 15 +- 3 (stat.) +5 -3 (sys.) mb..
481. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A search for high-mass resonances decaying to tau+tau- in pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2013.01.040, 719, 242-260, 2013.02, This Letter presents a search for high-mass resonances decaying into tau+tau- final states using proton-proton collisions at sqrt(s) = 7 TeV produced by the Large Hadron Collider. The data were recorded with the ATLAS detector and correspond to an integrated luminosity of 4.6 inverse femtobarns. No statistically significant excess above the Standard Model expectation is observed; 95% credibility upper limits are set on the cross section times branching fraction of Z' resonances decaying into tau+tau- pairs as a function of the resonance mass. As a result, Z' bosons of the Sequential Standard Model with masses less than 1.40 TeV are excluded at 95% credibility..
482. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for long-lived, heavy particles in final states with a muon and multi-track displaced vertex in proton-proton collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2013.01.042, 719, 280-298, 2013.02, Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. In this Letter, results are presented of a search for such particles, which decay at a significant distance from their production point, using a final state containing charged hadrons and an associated muon. This analysis uses a data sample of proton-proton collisions at sqrt(s)= 7 TeV corresponding to an integrated luminosity of 4.4 fb-1 collected in 2011 by the ATLAS detector operating at the Large Hadron Collider. Results are interpreted in the context of R-parity violating supersymmetric scenarios. No events in the signal region are observed and limits are set on the production cross section for supersymmetric particles, multiplied by the square of the branching ratio for a neutralino to decay to charged hadrons and a muon, as a function of the neutralino lifetime. To allow these limits to be used in a variety of models, they are presented for a range of squark and neutralino masses..
483. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for supersymmetry in events with photons, bottom quarks, and missing transverse momentum in proton-proton collisions at a centre-of-mass energy of 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2013.01.041, 719, 261-279, 2013.02, A search has been performed for the experimental signature of an isolated photon with high transverse momentum, at least one jet identified as originating from a bottom quark, and high missing transverse momentum. Such a final state may originate from supersymmetric models with gauge-mediated supersymmetry breaking in events in which one of a pair of higgsino-like neutralinos decays into a photon and a gravitino while the other decays into a Higgs boson and a gravitino. The search is performed using the full dataset of 7 TeV proton-proton collisions recorded with the ATLAS detector at the LHC in 2011, corresponding to an integrated luminosity of 4.7 fb-1. A total of 7 candidate events are observed while 7.5 pm 2.2 events are expected from the Standard Model background. The results of the search are interpreted in the context of general gauge mediation to exclude certain regions of a benchmark plane for higgsino-like neutralino production..
484. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the neutral Higgs bosons of the Minimal Supersymmetric Standard Model in pp collisions at √s =7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP02(2013)095, 2013, 02, 095, 2013.02, A search for neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) is reported. The analysis is based on a sample of proton-proton collisions at a centre-of-mass energy of 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. The data were recorded in 2011 and correspond to an integrated luminosity of 4.7 fb-1 to 4.8 fb-1. Higgs boson decays into oppositely-charged muon or tau lepton pairs are considered for final states requiring either the presence or absence of b-jets. No statistically significant excess over the expected background is observed and exclusion limits at the 95% confidence level are derived. The exclusion limits are for the production cross-section of a generic neutral Higgs boson, phi, as a function of the Higgs boson mass and for h/H/A production in the MSSM as a function of the parameters mA and tanbeta in the mh-max scenario for mA in the range of 90 GeV to 500 GeV..
485. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A Search for Prompt Lepton-Jets in pp Collisions at √s = 7 TeV with the ATLAS Detector, Phys. Lett. B, 10.1016/j.physletb.2013.01.034, 719, 299-317, 2013.02, We present a search for a light (mass < 2 GeV) boson predicted by Hidden Valley supersymmetric models that decays into a final state consisting of collimated muons or electrons, denoted "lepton-jets". The analysis uses 5fb-1 of sqrt(s) = 7 TeV proton--proton collision data recorded by the ATLAS detector at the Large Hadron Collider to search for the following signatures: single lepton-jets with at least four muons; pairs of lepton-jets, each with two or more muons; and pairs of lepton-jets with two or more electrons. This study finds no statistically significant deviation from the Standard Model prediction and places 95% confidence-level exclusion limits on the production cross section times branching ratio of light bosons for several parameter sets of a Hidden Valley model..
486. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the flavour composition of dijet events in pp collisions at √s =7 TeV with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-013-2301-5, 73, 2301, 2013.02, This paper describes a measurement of the flavour composition of dijet events produced in pp collisions at sqrt{s}=7 TeV using the ATLAS detector. The measurement uses the full 2010 data sample, corresponding to an integrated luminosity of 39 pb^-1. Six possible combinations of light, charm and bottom jets are identified in the dijet events, where the jet flavour is defined by the presence of bottom, charm or solely light flavour hadrons in the jet. Kinematic variables, based on the properties of displaced decay vertices and optimised for jet flavour identification, are used in a multidimensional template fit to measure the fractions of these dijet flavour states as functions of the leading jet transverse momentum in the range 40 GeV to 500 GeV and jet rapidity |y| < 2.1. The fit results agree with the predictions of leading- and next-to-leading-order calculations, with the exception of the dijet fraction composed of bottom and light flavour jets, which is underestimated by all models at large transverse jet momenta. The ability to identify jets containing two b-hadrons, originating from e.g. gluon splitting, is demonstrated. The difference between bottom jet production rates in leading and subleading jets is consistent with the next-to-leading-order predictions..
487. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the Jet Size Dependence of Inclusive Jet Suppression in Lead-Lead Collisions at √sNN = 2.76 TeV with the ATLAS Detector, Phys. Lett. B, 10.1016/j.physletb.2013.01.024, 719, 220-241, 2013.02, Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC. .
488. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the Λb lifetime and mass in the ATLAS experiment, Phys. Rev. D, 10.1103/PhysRevD.87.032002, 87, 032002, 2013.02, A measurement of the Lambda_b lifetime and mass in the decay channel Lambda_b -> J/psi(mu^+ mu^-) Lambda^0(p pi^-) is presented. The analysis uses a signal sample of about 2200 Lambda_b and anti-Lambda_b decays that are reconstructed in 4.9 fb^-1 of ATLAS pp collision data collected in 2011 at the LHC center-of-mass energy of 7 TeV. A simultaneous mass and decay time maximum likelihood fit is used to extract the Lambda_b lifetime and mass. They are measured to be tau(Lambda_b) = 1.449 +/- 0.036(stat) +/- 0.017(syst) ps and m(Lambda_b) = 5619.7 +/- 0.7(stat) +/- 1.1(syst) MeV. .
489. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena in the WW to l nu l' nu' final state in pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2012.11.040, 718, 860-878, 2013.01, This Letter reports a search for a heavy particle that decays to WW using events produced in pp collisions at sqrt(s) = 7 TeV. The data were recorded in 2011 by the ATLAS detector and correspond to an integrated luminosity of 4.7 fb-1. WW to l nu l' nu'(l, l' = e or mu) final states are considered and the distribution of the transverse mass of the WW candidates is found to be consistent with Standard Model expectations. Upper limits on the production cross section times branching ratio into W boson pairs are set for Randall-Sundrum and bulk Randall-Sundrum gravitons, which result in observed 95% CL lower limits on the masses of the two particles of 1.23 TeV and 0.84 TeV, respectively..
490. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for direct slepton and gaugino production in final states with two leptons and missing transverse momentum with the ATLAS detector in pp collisions at √s = 7 TeV, Phys. Lett. B, 10.1016/j.physletb.2012.11.058, 718, 879-901, 2013.01, A search for the electroweak pair production of charged sleptons and weak gauginos decaying into final states with two leptons is performed using 4.7 fb-1 of proton-proton collision data at sqrt(s)=7 TeV recorded with the ATLAS experiment at the Large Hadron Collider. No significant excesses are observed with respect to the prediction from Standard Model processes. In the scenario of direct slepton production, if the sleptons decay directly into the lightest neutralino, left-handed slepton masses between 85 and 195 GeV are excluded at 95% confidence level for a 20 GeV neutralino. Chargino masses between 110 and 340 GeV are excluded in the scenario of direct production of wino-like chargino pairs decaying into the lightest neutralino via an intermediate on-shell charged slepton for a 10 GeV neutralino. The results are also interpreted in the framework of the phenomenological minimal supersymmetric Standard Model..
491. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2012.11.039, 718, 841-859, 2013.01, A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb-1 of sqrt(s) = 7 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results..
492. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for pair production of heavy top-like quarks decaying to a high-p_T W boson and a b quark in the lepton plus jets final state at √s =7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2012.11.071, 718, 1284-1302, 2013.01, A search is presented for production of a heavy up-type quark (t') together with its antiparticle, assuming a significant branching ratio for subsequent decay into a W boson and a b quark. The search is based on 4.7 fb^-1 of pp collisions at sqrt(s)=7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. Data are analyzed in the lepton+jets final state, characterized by a high-transverse-momentum isolated electron or muon, large missing transverse momentum and at least three jets. The analysis strategy relies on the substantial boost of the W bosons in the t't'bar signal when mt'>=400 GeV. No significant excess of events above the Standard Model expectation is observed and the result of the search is interpreted in the context of fourth-generation and vector-like quark models. Under the assumption of a branching ratio BR(t'->Wb)=1, a fourth-generation t' quark with mass lower than 656 GeV is excluded at 95% confidence level. In addition, in light of the recent discovery of a new boson of mass ~126 GeV at the LHC, upper limits are derived in the two-dimensional plane of BR(t'->Wb) versus BR(t'->Ht), where H is the Standard Model Higgs boson, for vector-like quarks of various masses..
493. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of Z boson production in Pb+Pb collisions at √sNN=2.76TeV with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.110.022301, 110, 022301, 2013.01, The ATLAS experiment has observed 1995 Z boson candidates in data corresponding to 0.15 inverse nb of integrated luminosity obtained in the 2011 LHC Pb+Pb run at sqrt(s_NN)=2.76 TeV. The Z bosons are reconstructed via di-electron and di-muon decay channels, with a background contamination of less than 3%. Results from the two channels are consistent and are combined. Within the statistical and systematic uncertainties, the per-event Z boson yield is proportional to the number of binary collisions estimated by the Glauber model. The elliptic anisotropy of the azimuthal distribution of the Z boson with respect to the event plane is found to be consistent with zero..
494. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for contact interactions and large extra dimensions in dilepton events from pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.87.015010, 87, 015010, 2013.01, A search for non-resonant new phenomena, originating from either contact interactions or large extra spatial dimensions, has been carried out using events with two isolated electrons or muons. These events, produced at the LHC in proton-proton collisions at sqrt(s) = 7 TeV, were recorded by the ATLAS detector. The data sample, collected throughout 2011, corresponds to an integrated luminosity of 4.9 and 5.0 fb-1 in the e+e- and mu+mu- channels, respectively. No significant deviations from the Standard Model expectation are observed. Using a Bayesian approach, 95% confidence limit lower limits ranging from 9.0 to 13.9 TeV are placed on the energy scale of llqq contact interactions in the left-left isoscalar model. Lower limits ranging from 2.4 to 3.9 TeV are also set on the string scale in large extra dimension models. After combination of these limits with results from a similar search in the diphoton channel, slightly more stringent limits are obtained..
495. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of isolated-photon pair production in pp collisions at √s = 7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP01(2013)086, 2013, 01, 086, 2013.01, The ATLAS experiment at the LHC has measured the production cross section of events with two isolated photons in the final state, in proton-proton collisions at sqrt(s) = 7 TeV. The full data set collected in 2011, corresponding to an integrated luminosity of 4.9 fb-1, is used. The amount of background, from hadronic jets and isolated electrons, is estimated with data-driven techniques and subtracted. The total cross section, for two isolated photons with transverse energies above 25 GeV and 22 GeV respectively, in the acceptance of the electromagnetic calorimeter (|eta|<1.37 and 1.52<|eta|<2.37) and with an angular separation Delta R>0.4, is 44.0 (+3.2) (-4.2) pb. The differential cross sections as a function of the di-photon invariant mass, transverse momentum, azimuthal separation, and cosine of the polar angle of the largest transverse energy photon in the Collins--Soper di-photon rest frame are also measured. The results are compared to the prediction of leading-order parton-shower and next-to-leading-order and next-to-next-to-leading-order parton-level generators..
496. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for resonances decaying into top-quark pairs using fully hadronic decays in pp collisions with ATLAS at √s = 7 TeV, JHEP, 10.1007/JHEP01(2013)116, 2013, 01, 116, 2013.01, A search for resonances produced in 7 TeV proton-proton collisions and decaying into top-quark pairs is described. In this Letter events where the top-quark decay produces two massive jets with large transverse momenta recorded with the ATLAS detector at the Large Hadron Collider are considered. Two techniques that rely on jet substructure are used to separate top-quark jets from those arising from light quarks and gluons. In addition, each massive jet is required to have evidence of an associated bottom-quark decay. The data are consistent with the Standard Model, and limits can be set on the production cross section times branching fraction of a Z' boson and a Kaluza-Klein gluon resonance. These limits exclude, at the 95% credibility level, Z' bosons with masses 0.70-1.00 TeV as well as 1.28-1.32 TeV and Kaluza-Klein gluons with masses 0.70-1.62 TeV..
497. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for pair-produced massive coloured scalars in four-jet final states with the ATLAS detector in proton-proton collisions at s√=7 TeV, Eur. Phys. J. C, 10.1140/epjc/s10052-012-2263-z, 73, 2263, 2013.01, A search for pair-produced massive coloured scalar particles decaying to a four-jet final state is performed by the ATLAS experiment at the LHC in proton-proton collisions at sqrt(s) = 7 TeV. The analysed data sample corresponds to an integrated luminosity of 4.6 /fb. No deviation from the Standard Model is observed in the invariant mass spectrum of the two-jet pairs. A limit on the scalar gluon pair production cross-section of 70 pb (10 pb) is obtained at the 95% confidence level for a scalar gluon mass of 150 GeV (350 GeV). Interpreting these results as mass limits on scalar gluons, masses ranging from 150 GeV to 287 GeV are excluded at the 95% confidence level..
498. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for direct chargino production in anomaly-mediated supersymmetry breaking models based on a disappearing-track signature in pp collisions at √s = 7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP01(2013)131, 2013, 01, 131, 2013.01, A search for direct chargino production in anomaly-mediated supersymmetry breaking scenarios is performed in pp collisions at sqrt(s) = 7 TeV using 4.7 fb^-1 of data collected with the ATLAS experiment at the LHC. In these models, the lightest chargino is predicted to have a lifetime long enough to be detected in the tracking detectors of collider experiments. This analysis explores such models by searching for chargino decays that result in tracks with few associated hits in the outer region of the tracking system. The transverse-momentum spectrum of candidate tracks is found to be consistent with the expectation from the Standard Model background processes and constraints on chargino properties are obtained..
499. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), ATLAS search for new phenomena in dijet mass and angular distributions using pp collisions at √s = 7 TeV, JHEP, 10.1007/JHEP01(2013)029, 2013, 01, 029, 2013.01, Mass and angular distributions of dijets produced in LHC proton-proton collisions at a centre-of-mass energy sqrt(s)=7 TeV have been studied with the ATLAS detector using the full 2011 data set with an integrated luminosity of 4.8/fb. Dijet masses up to 4.0 TeV have been probed. No resonance-like features have been observed in the dijet mass spectrum, and all angular distributions are consistent with the predictions of QCD. Exclusion limits on six hypotheses of new phenomena have been set at 95% CL in terms of mass or energy scale, as appropriate. These hypotheses include excited quarks below 2.83 TeV, colour octet scalars below 1.86 TeV, heavy W bosons below 1.68 TeV, string resonances below 3.61 TeV, quantum black holes with six extra space-time dimensions for quantum gravity scales below 4.11 TeV, and quark contact interactions below a compositeness scale of 7.6 TeV in a destructive interference scenario..
500. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for dark matter candidates and large extra dimensions in events with a photon and missing transverse momentum in pp collision data at √s = 7 TeV with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.110.011802, 110, 011802, 2013.01, Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum in proton-proton collisions at sqrt(s)=7 TeV are reported. Data collected by the ATLAS experiment at the LHC corresponding to an integrated luminosity of 4.6 fb-1 are used. Good agreement is observed between the data and the Standard Model predictions. The results are translated into exclusion limits on models with large extra spatial dimensions and on pair production of weakly interacting dark matter candidates..
501. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using 4.7 fb-1 of √s = 7 TeV proton-proton collision data, Phys. Rev. D, 10.1103/PhysRevD.87.012008, 87, 012008, 2013.01, A search for squarks and gluinos in final states containing jets, missing transverse momentum and no high-pT electrons or muons is presented. The data represent the complete sample recorded in 2011 by the ATLAS experiment in 7 TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of 4.7 fb^-1. No excess above the Standard Model background expectation is observed. Gluino masses below 860 GeV and squark masses below 1320 GeV are excluded at the 95% confidence level in simplified models containing only squarks of the first two generations, a gluino octet and a massless neutralino, for squark or gluino masses below 2 TeV, respectively. Squarks and gluinos with equal masses below 1410 GeV are excluded. In MSUGRA/CMSSM models with tan beta = 10, A_0 = 0 and mu > 0, squarks and gluinos of equal mass are excluded for masses below 1360 GeV. Constraints are also placed on the parameter space of SUSY models with compressed spectra. These limits considerably extend the region of supersymmetric parameter space excluded by previous measurements with the ATLAS detector. .
502. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of top quark pair relative differential cross-sections with ATLAS in pp collisions at √s = 7 TeV, Eur. Phys. J. C, 10.1140/epjc/s10052-012-2261-1, 73, 2261, 2013.01, Measurements are presented of differential cross-sections for top quark pair production in pp collisions at sqrt(s) = 7 TeV relative to the total inclusive top quark pair production cross-section. A data sample of 2.05/fb recorded by the ATLAS detector at the Large Hadron Collider is used. Relative differential cross-sections are derived as a function of the invariant mass, the transverse momentum and the rapidity of the top quark pair system. Events are selected in the lepton (electron or muon) + jets channel. The background-subtracted differential distributions are corrected for detector effects, normalized to the total inclusive top quark pair production cross-section and compared to theoretical predictions. The measurement uncertainties range typically between 10% and 20% and are generally dominated by systematic effects. No significant deviations from the Standard Model expectations are observed. .
503. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Diphoton Events with Large Missing Transverse Momentum in 5 fb-1 of 7 TeV Proton-Proton Collision Data with the ATLAS Detector, Phys. Lett. B, 10.1016/j.physletb.2012.10.069, 718, 411-430, 2012.12, A search for diphoton events with large missing transverse momentum has been performed using proton-proton collision data at sqrt(s) = 7 TeV recorded with the ATLAS detector, corresponding to an integrated luminosity of 4.8 fb^-1. No excess of events was observed above the Standard Model prediction and model-dependent 95% confidence level exclusion limits are set. In the context of a generalised model of gauge-mediated supersymmetry breaking with a bino-like lightest neutralino of mass above 50 GeV, gluinos (squarks) below 1.07 TeV (0.87 TeV) are excluded, while a breaking scale Lambda below 196 TeV is excluded for a minimal model of gauge-mediated supersymmetry breaking. For a specific model with one universal extra dimension, compactification scales 1/R < 1.40 TeV are excluded. These limits provide the most stringent tests of these models to date..
504. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), ATLAS search for a heavy gauge boson decaying to a charged lepton and a neutrino in pp collisions at √s = 7 TeV, Eur. Phys. J. C, 10.1140/epjc/s10052-012-2241-5, 72, 2241, 2012.12, The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (W'), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a centre-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.7 fb-1. No excess beyond Standard Model expectations is observed. A W' with Sequential Standard Model couplings is excluded at the 95% credibility level for masses up to 2.55 TeV. Excited chiral bosons (W*) with equivalent coupling strength are excluded for masses up to 2.42 TeV..
505. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for pair production of massive particles decaying into three quarks with the ATLAS detector in √s =7 TeV pp collisions at the LHC, JHEP, 10.1007/JHEP12(2012)086, 2012, 12, 086, 2012.12, A search is conducted for hadronic three-body decays of a new massive coloured particle in sqrt(s) = 7 TeV pp collisions at the LHC using an integrated luminosity of 4.6/fb collected by the ATLAS detector. Supersymmetric gluino pair production in the context of a model with R-parity violation is used as a benchmark scenario. The analysis is divided into two search channels, each optimised separately for their sensitivity to high-mass and low-mass gluino production. The first search channel uses a stringent selection on the transverse momentum of the six leading jets and is performed as a counting experiment. The second search channel focuses on low-mass gluinos produced with a large boost. Large-radius jets are selected and the invariant mass of each of the two leading jets is used as a discriminant between the signal and the background. The results are found to be consistent with Standard Model expectations and limits are set on the allowed gluino mass..
506. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for doubly-charged Higgs bosons in like-sign dilepton final states at √s =7 TeV with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-012-2244-2, 72, 2244, 2012.12, A search for doubly-charged Higgs bosons decaying to pairs of electrons and/or muons is presented. The search is performed using a data sample corresponding to an integrated luminosity of 4.7 fb-1 of pp collisions at sqrt(s) = 7 TeV collected by the ATLAS detector at the LHC. Pairs of prompt, isolated, high-pT leptons with the same electric charge (ee, emu, mumu) are selected, and their invariant mass distribution is searched for a narrow resonance. No significant excess over Standard Model background expectations is observed, and limits are placed on the cross section times branching ratio for pair production of doubly-charged Higgs bosons. The masses of doubly-charged Higgs bosons are constrained depending on the branching ratio into these leptonic final states. Assuming pair production, coupling to left-handed fermions, and a branching ratio of 100% for each final state, masses below 409 GeV, 375 GeV, and 398 GeV are excluded for ee, emu, mumu, respectively..
507. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A Massive Particle Consistent with the Standard Model Higgs Boson observed with the ATLAS Detector at the Large Hadron Collider, Science, 10.1126/science.1232005, 338, 6114, 1576-1582, 2012.12, Nearly 50 years ago, theoretical physicists proposed that a field permeates the universe and gives energy to the vacuum. This field was required to explain why some, but not all, fundamental particles have mass. Numerous precision measurements during recent decades have provided indirect support for the existence of this field, but one crucial prediction of this theory has remained unconfirmed despite 30 years of experimental searches: the existence of a massive particle, the standard model Higgs boson. The ATLAS experiment at the Large Hadron Collider at CERN has now observed the production of a new particle with a mass of 126 giga–electron volts and decay signatures consistent with those expected for the Higgs particle. This result is strong support for the standard model of particle physics, including the presence of this vacuum field. The existence and properties of the newly discovered particle may also have consequences beyond the standard model itself..
508. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for anomalous production of prompt like-sign lepton pairs at √s =7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP12(2012)007, 2012, 12, 007, 2012.12, An inclusive search for anomalous production of two prompt, isolated leptons with the same electric charge is presented. The search is performed in a data sample corresponding to 4.7 fb-1 of integrated luminosity collected in 2011 at sqrt(s) = 7 TeV with the ATLAS detector at the LHC. Pairs of leptons (ee, emu, and mumu) with large transverse momentum are selected, and the dilepton invariant mass distribution is examined for any deviation from the Standard Model expectation. No excess is found, and upper limits on the production cross section of like-sign lepton pairs from physics processes beyond the Standard Model are placed as a function of the dilepton invariant mass within a fiducial region close to the experimental selection criteria. The 95% confidence level upper limits on the cross section of anomalous ee, emu, or mumu production range between 1.7 fb and 64 fb depending on the dilepton mass and flavour combination..
509. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for R-parity-violating supersymmetry in events with four or more leptons in √s=7 TeV pp collisions with the ATLAS detector, JHEP, 10.1007/JHEP12(2012)124, 2012, 12, 124, 2012.12, A search for new phenomena in final states with four or more leptons (electrons or muons) is presented. The analysis is based on 4.7 fb^-1 of sqrt(s) = 7 TeV proton-proton collisions delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in two signal regions: one that requires moderate values of missing transverse momentum and another that requires large effective mass. The results are interpreted in a simplified model of R-parity-violating supersymmetry in which a 95% CL exclusion region is set for charged wino masses up to 540 GeV. In an R-parity-violating MSUGRA/CMSSM model, values of m_1/2 up to 820 GeV are excluded for 10
510. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Time dependent angular analysis of the decay Bs→J/ψ phi and extraction of Delta Gammas and the CP-violating weak phase phis by ATLAS, JHEP, 10.1007/JHEP12(2012)072, 2012, 12, 072, 2012.12, A measurement of Bs J/psi phi decay parameters, including the CP-violating weak phase phi_s and the decay width difference Delta Gamma_s is reported, using 4.9 fb-1 of integrated luminosity collected in 2011 by the ATLAS detector from LHC pp collisions at a centre- of-mass energy sqrt(s) = 7 TeV. The mean decay width Gamma_s and the transversity amplitudes |A0(0)|^2 and |A||(0)|^2 are also measured. The values reported for these parameters are: phi_s = 0.22 ± 0.41 (stat.) ± 0.10 (syst.) rad, Delta Gamma_s = 0.053 ± 0.021 (stat.) ± 0.010 (syst.) ps-1 Gamma_s = 0.677 ± 0.007 (stat.) ± 0.004 (syst.) ps-1, |A0(0)|^2 = 0.528 ± 0.006 (stat.) ± 0.009 (syst.), |A||(0)|^2 = 0.220 ± 0.008 (stat.) ± 0.007 (syst.) where the values quoted for phi_s and Delta Gamma_s correspond to the solution compatible with the external measurements to which the strong phase delta perpendicular is constrained and where Delta Gamma_s is constrained to be positive. The fraction of S-wave KK or f0 contamination through the decays Bs -> J/psi K+K-(f0) is measured as well and is found to be consistent with zero. Results for phi_s and Delta Gamma_s are also presented as 68%, 90% and 95% likelihood contours, which show agreement with Standard Model expectations. .
511. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for magnetic monopoles in √s = 7 TeV pp collisions with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.109.261803, 109, 261803, 2012.12, This Letter presents a search for magnetic monopoles with the ATLAS detector at the CERN Large Hadron Collider using an integrated luminosity of 2.0 fb^-1 of pp collisions recorded at a center-of-mass energy of sqrt(s)=7 TeV. No event is found in the signal region, leading to an upper limit on the production cross section at 95% confidence level of 1.6/epsilon fb for Dirac magnetic monopoles with the minimum unit magnetic charge and with mass between 200 GeV and 1500 GeV, where epsilon is the monopole reconstruction efficiency. The efficiency epsilon is high and uniform in the fiducial region given by pseudorapidity |eta|<1.37 and transverse kinetic energy 600-700
512. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Standard Model Higgs boson produced in association with a vector boson and decaying to a b-quark pair with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2012.10.061, 718, 369-390, 2012.12, This Letter presents the results of a direct search with the ATLAS detector at the LHC for a Standard Model Higgs boson of mass 110 < m(H) < 130 GeV produced in association with a W or Z boson and decaying to bb. Three decay channels are considered: ZH->llbb, WH->lvbb, and ZH->vvbb, where l corresponds to an electron or a muon. No evidence for Higgs boson production is observed in a dataset of 7 TeV pp collisions corresponding to 4.7/fb of integrated luminosity collected by ATLAS in 2011. Exclusion limits on Higgs boson production, at the 95% confidence level, of 2.5 to 5.5 times the Standard Model cross section are obtained in the mass range 110 - 130 GeV. The expected exclusion limits range between 2.5 and 4.9 for the same mass interval. .
513. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Higgs boson in the H→WW→lnujj decay channel at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2012.10.066, 718, 391-410, 2012.12, Search for the Higgs boson in the H→WW→lnujj decay channel at √s = 7 TeV with the ATLAS detector.
514. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for direct top squark pair production in final states with one isolated lepton, jets, and missing transverse momentum in √s = 7 TeV pp collisions using 4.7 fb-1of ATLAS data, Phys. Rev. Lett., 10.1103/PhysRevLett.109.211803, 109, 211803, 2012.11, A search is presented for direct top squark pair production in final states with one isolated electron or muon, jets, and missing transverse momentum in proton-proton collisions at sqrt(s) = 7 TeV. The measurement is based on 4.7 fb-1 of data collected with the ATLAS detector at the LHC. Each top squark is assumed to decay to a top quark and the lightest supersymmetric particle (LSP). The data are found to be consistent with Standard Model expectations. Top squark masses between 230 GeV and 440 GeV are excluded with 95% confidence for massless LSPs, and top squark masses around 400 GeV are excluded for LSP masses up to 125 GeV..
515. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for light scalar top quark pair production in final states with two leptons with the ATLAS detector in √s = 7 TeV proton-proton collisions, Eur. Phys. J. C, 10.1140/epjc/s10052-012-2237-1, 72, 2237, 2012.11, A search is presented for the pair production of light scalar top quarks in sqrt(s) = 7 TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider. This analysis uses the full data sample collected during 2011 that corresponds to a total integrated luminosity of 4.7 fb-1. Light scalar top quarks are searched for in events with two opposite-sign leptons (e, mu), large missing transverse momentum and at least one jet in the final state. No excess over Standard Model expectations is found, and the results are interpreted under the assumption that the light scalar top decays to a b-quark in addition to an on-shell chargino whose decay occurs through a virtual W boson. If the chargino mass is 106 GeV, light scalar top quark masses up to 130 GeV are excluded for neutralino masses below 70 GeV..
516. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Further search for supersymmetry at √s = 7 TeV in final states with jets, missing transverse momentum and isolated leptons with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.86.092002, 86, 092002, 2012.11, This work presents a new inclusive search for supersymmetry (SUSY) by the ATLAS experiment at the LHC in proton-proton collisions at a center-of-mass energy sqrt(s) = 7 TeV in final states with jets, missing transverse momentum and one or more isolated electrons and/or muons. The search is based on data from the full 2011 data-taking period, corresponding to an integrated luminosity of 4.7 inverse fb. Single- and multi-lepton channels are treated together in one analysis. An increase in sensitivity is obtained by simultaneously fitting the number of events in statistically independent signal regions, and the shapes of distributions within those regions. A dedicated signal region is introduced to be sensitive to decay cascades of SUSY particles with small mass differences ("compressed SUSY"). Background uncertainties are constrained by fitting to the jet multiplicity distribution in background control regions. Observations are consistent with Standard Model expectations, and limits are set or extended on a number of SUSY models..
517. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of the pseudorapidity dependence of the total transverse energy in proton-proton collisions at √s = 7 TeV with ATLAS, JHEP, 10.1007/JHEP11(2012)033, 2012, 11, 033, 2012.11, This paper describes measurements of the sum of the transverse energy of particles as a function of particle pseudorapidity, eta, in proton-proton collisions at a centre-of-mass energy, sqrt(s) = 7 TeV using the ATLAS detector at the Large Hadron Collider. The measurements are performed in the region |eta| < 4.8 for two event classes: those requiring the presence of particles with a low transverse momentum and those requiring particles with a significant transverse momentum. In the second dataset measurements are made in the region transverse to the hard scatter. The distributions are compared to the predictions of various Monte Carlo event generators, which generally tend to underestimate the amount of transverse energy at high |eta|..
518. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for high-mass resonances decaying to dilepton final states in pp collisions at √s = 7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP11(2012)138, 2012, 11, 138, 2012.11, The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to an electron-positron pair or a muon-antimuon pair. The search is sensitive to heavy neutral Z' gauge bosons, Randall-Sundrum gravitons, Z* bosons, techni-mesons, Kaluza-Klein Z/gamma bosons, and bosons predicted by Torsion models. Results are presented based on an analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.9/fb in the dielectron channel and 5.0/fb in the dimuon channel. A Z' boson with Standard Model-like couplings is excluded at 95 percent confidence level for masses below 2.22 TeV. A Randall-Sundrum graviton with coupling k/Mbar = 0.1 is excluded at 95 percent confidence level for masses below 2.16 TeV. Limits on the other models are also presented, including Technicolor and Minimal Z' Models..
519. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a heavy top-quark partner in final states with two leptons with the ATLAS detector at the LHC, JHEP, 10.1007/JHEP11(2012)094, 2012, 11, 094, 2012.11, The results of a search for direct pair production of heavy top-quark partners in 4.7 fb-1 of integrated luminosity from pp collisions at sqrt(s) = 7 TeV collected by the ATLAS detector at the LHC are reported. Heavy top-quark partners decaying into a top quark and a neutral non-interacting particle are searched for in events with two leptons in the final state. No excess above the Standard Model expectation is observed. Limits are placed on the mass of a supersymmetric scalar top and of a spin-1/2 top-quark partner. A spin-1/2 top-quark partner with a mass between 300 GeV and 480 GeV, decaying to a top quark and a neutral non-interacting particle lighter than 100 GeV, is excluded at 95% confidence level..
520. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of event shapes at large momentum transfer with the ATLAS detector in pp collisions at √s = 7 TeV, Eur. Phys. J. C, 10.1140/epjc/s10052-012-2211-y, 72, 2211, 2012.11, A measurement of event shape variables is presented for large momentum transfer proton-proton collisions using the ATLAS detector at the Large Hadron Collider. Six event shape variables calculated using hadronic jets are studied in inclusive multi-jet events in 35 pb^-1 of integrated luminosity at a center-of-mass energy of sqrt(s) = 7 TeV. These measurements are compared to predictions by three Monte Carlo event generators containing leading-logarithmic parton showers matched to leading order matrix elements for 2 to 2 and 2 to n (n=2,...6) scattering. Measurements of the third-jet resolution parameter, aplanarity, thrust, sphericity, and transverse sphericity are generally well described. The mean value of each event shape variable is evaluated as a function of the average momentum of the two leading jets pT1 and pT2, with a mean pT approaching 1 TeV..
521. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the b-hadron production cross section using decays to D*muX final states in pp collisions at √s = 7 TeV with the ATLAS detector, Nucl. Phys. B, 10.1016/j.nuclphysb.2012.07.009, 864, 341-381, 2012.11, The b-hadron production cross section is measured with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV, using 3.3 pb^-1 of integrated luminosity, collected during the 2010 LHC run. The b-hadrons are selected by partially reconstructing D*muX final states. Differential cross sections are measured as functions of the transverse momentum and pseudorapidity. The measured production cross section for a b-hadron with pT>9 GeV and |eta|<2.5 is 32.7 pm 0.8 (stat) ^{+4.5}_{-6.8} (syst) ub, higher than the next-to-leading-order QCD predictions but consistent within the experimental and theoretical uncertainties..
522. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Supersymmetry in Events with Large Missing Transverse Momentum, Jets, and at Least One Tau Lepton in 7 TeV Proton-Proton Collision Data with the ATLAS Detector, Eur. Phys. J. C, 10.1140/epjc/s10052-012-2215-7, 72, 2215, 2012.11, A search for supersymmetry (SUSY) in events with large missing transverse momentum, jets, and at least one hadronically decaying tau lepton, with zero or one additional light lepton (e/mu), has been performed using 4.7 fb-1 of proton-proton collision data at sqrt(s) = 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. No excess above the Standard Model background expectation is observed and a 95% confidence level visible cross-section upper limit for new phenomena is set. In the framework of gauge-mediated SUSY-breaking models, lower limits on the mass scale Lambda are set at 54 TeV in the regions where the stau is the next-to-lightest SUSY particle (tan(beta) > 20). These limits provide the most stringent tests to date of GMSB models in a large part of the parameter space considered..
523. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for resonant top quark plus jet production in ttbar + jets events with the ATLAS detector in pp collisions at √s = 7 TeV, Phys. Rev. D, 10.1103/PhysRevD.86.091103, 86, 091103, 2012.11, This paper presents a search for a new heavy particle produced in association with a top or antitop quark. Two models in which the new heavy particle is a color singlet or a color triplet are considered, decaying respectively to tbarq or tq, leading to a resonance within the ttbar + jets signature. The full 2011 ATLAS pp collision dataset from the LHC (4.7 fb-1) is used to search for ttbar events produced in association with jets, in which one of the W bosons from the top quarks decays leptonically and the other decays hadronically. The data are consistent with the Standard Model expectation, and a new particle with mass below 430 GeV for both W boson and color triplet models is excluded at 95% confidence level, assuming unit right-handed coupling..
524. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a supersymmetric partner to the top quark in final states with jets and missing transverse energy at √s = 7 TeV with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.109.211802, 109 , 211802, 2012.11, A search for direct pair production of supersymmetric top squarks (stop_1) is presented, assuming the stop_1 decays into a top quark and the lightest supersymmetric particle, neutralino_1, and that both top quarks decay to purely hadronic final states. A total of 16 (4) events are observed compared to a predicted Standard Model background of 13.5+3.7-3.6 (4.4+1.7-1.3) events in two signal regions based on int(Ldt) = 4.7 fb^-1 of pp collision data taken at sqrt(s) = 7 TeV with the ATLAS detector at the LHC. An exclusion region in the stop_1 versus neutralino_1 mass plane is evaluated: 370
525. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the t-channel single top-quark production cross section in pp collisions at root s=7 TeV with the ATLAS detector, PHYSICS LETTERS B, 10.1016/j.physletb.2012.09.031, 717, 4-5, 330-350, 2012.10.
526. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of W gamma and Z gamma production cross sections in pp collisions at root s=7 TeV and limits on anomalous triple gauge couplings with the ATLAS detector, PHYSICS LETTERS B, 10.1016/j.physletb.2012.09.017, 717, 1-3, 49-69, 2012.10.
527. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a standard model Higgs boson in the H -> ZZ -> l(+)l(-) nu(nu)over-bar decay channel using 4.7 fb(-1) of root s=7 TeV data with the ATLAS detector, PHYSICS LETTERS B, 10.1016/j.physletb.2012.09.016, 717, 1-3, 29-48, 2012.10.
528. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the top quark pair cross section with ATLAS in pp collisions at √s = 7 TeV using final states with an electron or a muon and a hadronically decaying tau lepton, Phys. Lett. B, 10.1016/j.physletb.2012.09.032, 717, 89-108, 2012.10, A measurement of the cross section of top quark pair production in proton-proton collisions recorded with the ATLAS detector at the LHC at a centre-of-mass energy of 7 TeV is reported. The data sample used corresponds to an integrated luminosity of 2.05 fb^-1. Events with an isolated electron or muon and a tau lepton decaying hadronically are used. In addition, a large missing transverse momentum and two or more energetic jets are required. At least one of the jets must be identified as originating from a b quark. The measured cross section, sigma_ttbar = 186+/- 13 (stat) +/- 20 (syst) +/- 7 (lum.) pb is in good agreement with the Standard Model prediction..
529. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of WZ Production in Proton-Proton Collisions at √s = 7 TeV with the ATLAS Detector, Eur. Phys. J. C, 10.1140/epjc/s10052-012-2173-0, 72, 2173, 2012.10, A study of WZ production in proton-proton collisions at sqrt(s) = 7 TeV is presented using data corresponding to an integrated luminosity of 4.6 fb^-1 collected with the ATLAS detector at the Large Hadron Collider in 2011. In total, 317 candidates, with a background expectation of 68+/-10 events, are observed in double-leptonic decay final states with electrons, muons and missing transverse momentum. The total cross-section is determined to be sigma_WZ(tot) = 19.0+1.4/-1.3(stat.)+/-0.9(syst.)+/-0.4(lumi.) pb, consistent with the Standard Model expectation of 17.6+1.1/-1.0 pb. Limits on anomalous triple gauge boson couplings are derived using the transverse momentum spectrum of Z bosons in the selected events. The cross section is also presented as a function of Z boson transverse momentum and diboson invariant mass. .
530. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Underlying event characteristics and their dependence on jet size of charged-particle jet events in pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.86.072004, 86, 072004, 2012.10, Distributions sensitive to the underlying event are studied in events containing one or more charged-particle jets produced in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector at the Large Hadron Collider (LHC). These measurements reflect 800 inverse microbarns of data taken during 2010. Jets are reconstructed using the antikt algorithm with radius parameter R varying between 0.2 and 1.0. Distributions of the charged-particle multiplicity, the scalar sum of the transverse momentum of charged particles, and the average charged-particle pT are measured as functions of pT^JET in regions transverse to and opposite the leading jet for 4 GeV < pT^JET < 100 GeV. In addition, the R-dependence of the mean values of these observables is studied. In the transverse region, both the multiplicity and the scalar sum of the transverse momentum at fixed pT^JET vary significantly with R, while the average charged-particle transverse momentum has a minimal dependence on R. Predictions from several Monte Carlo tunes have been compared to the data; the predictions from Pythia 6, based on tunes that have been determined using LHC data, show reasonable agreement with the data, including the dependence on R. Comparisons with other generators indicate that additional tuning of soft-QCD parameters is necessary for these generators. The measurements presented here provide a testing ground for further development of the Monte Carlo models. .
531. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for top and bottom squarks from gluino pair production in final states with missing transverse energy and at least three b-jets with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-012-2174-z, 72, 2174, 2012.10, This letter reports the results of a search for top and bottom squarks from gluino pair production in 4.7 fb^-1 of pp collisions at sqrt(s) = 7 TeV using the ATLAS detector at the LHC. The search is performed in events with large missing transverse momentum and at least three jets identified as originating from a b-quark. Exclusion limits are presented for a variety of gluino-mediated models with gluino masses up to 1 TeV excluded. .
532. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), ATLAS measurements of the properties of jets for boosted particle searches, Phys. Rev. D, 10.1103/PhysRevD.86.072006, 86, 072006, 2012.10, Measurements are presented of the properties of high transverse momentum jets, produced in proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV. The data correspond to an integrated luminosity of 35 pb^-1 and were collected with the ATLAS detector in 2010. Jet mass, width, eccentricity, planar flow and angularity are measured for jets reconstructed using the anti-kt algorithm with distance parameters R = 0.6 and 1.0, with transverse momentum pT > 300 GeV and pseudorapidity |eta| < 2. The measurements are compared to the expectations of Monte Carlo generators that match leading-logarithmic parton showers to leading-order, or next-to-leading-order, matrix elements. The generators describe the general features of the jets, although discrepancies are observed in some distributions. .
533. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a Standard Model Higgs in the mass range 200-600 GeV in the channel H → ZZ → llqq with with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2012.09.020, 717, 70-88, 2012.10, A search for a heavy Standard Model Higgs boson decaying via H->ZZ->llqq, where l=e or mu, is presented. The search uses a data set of pp collisions at sqrt(s) = 7 TeV, corresponding to an integrated luminosity of 4.7 fb^-1 collected in 2011 by the ATLAS detector at the CERN LHC. No significant excess of events above the estimated background is found. Upper limits at 95% confidence level on the production cross section of a Higgs boson with a mass in the range between 200 and 600 GeV are derived. A Standard Model Higgs boson with a mass in the range 300 <= mH <= 322 GeV or 353 <= mH <= 410 GeV is excluded at 95% CL. The corresponding expected exclusion range is 351 <= mH <= 404 GeV at 95% CL. .
534. C. Adloff, K. Kawagoe et al. (The CALICE collaboration), Hadronic energy resolution of a highly granular scintillator-steel hadron calorimeter using software compensation techniques, JOURNAL OF INSTRUMENTATION, 10.1088/1748-0221/7/09/P09017, 7, 2012.09.
535. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the azimuthal ordering of charged hadrons with the ATLAS detector, PHYSICAL REVIEW D, 10.1103/PhysRevD.86.052005, 86, 5, 2012.09.
536. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Evidence for the associated production of a W boson and a top quark in ATLAS at root s=7 TeV, PHYSICS LETTERS B, 10.1016/j.physletb.2012.08.011, 716, 1, 142-159, 2012.09.
537. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for TeV-scale gravity signatures in final states with leptons and jets with the ATLAS detector at root s=7 TeV, PHYSICS LETTERS B, 10.1016/j.physletb.2012.08.009, 716, 1, 122-141, 2012.09.
538. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for second generation scalar leptoquarks in pp collisions at root s=7 TeV with the ATLAS detector, EUROPEAN PHYSICAL JOURNAL C, 10.1140/epjc/s10052-012-2151-6, 72, 9, 2012.09.
539. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Standard Model Higgs boson in the H → WW → lvlv decay mode with 4.7 fb-1 of ATLAS data at √s = 7 TeV, Phys. Lett. B, 10.1016/j.physletb.2012.08.010, 716, 62-81, 2012.09, A search for the Standard Model Higgs boson in the H -> WW(*) -> l nu l nu (l = e, mu) decay mode is presented. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 4.7 /fb at a centre-of-mass energy of 7 TeV collected during 2011 with the ATLAS detector at the Large Hadron Collider. No significant excess of events over the expected background is observed. An upper bound is placed on the Higgs boson production cross section as a function of its mass. A Standard Model Higgs boson with mass in the range between 133 GeV and 261 GeV is excluded at 95% confidence level, while the expected exclusion range is from 127 GeV to 233 GeV..
540. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A search for flavour changing neutral currents in top-quark decays in pp collision data collected with the ATLAS detector at √s = 7 TeV, JHEP, 10.1007/JHEP09(2012)139, 2012, 09, 139, 2012.09, A search for flavour changing neutral current (FCNC) processes in top-quark decays by the ATLAS Collaboration is presented. Data collected from pp collisions at the LHC at a centre-of-mass energy of sqrt(s) = 7 TeV during 2011, corresponding to an integrated luminosity of 2.1 fb^-1, were used. A search was performed for top-quark pair-production events, with one top quark decaying through the t->Zq FCNC (q=u,c) channel, and the other through the Standard Model dominant mode t->Wb. Only the decays of the Z boson to charged leptons and leptonic W-boson decays were considered as signal. Consequently, the final-state topology is characterised by the presence of three isolated charged leptons, at least two jets and missing transverse momentum from the undetected neutrino. No evidence for an FCNC signal was found. An upper limit on the t->Zq branching ratio of BR(t->Zq)<0.73% is set at the 95% confidence level..
541. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a fermiophobic Higgs boson in the diphoton decay channel with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-012-2157-0, 72, 2157, 2012.09, A search for a fermiophobic Higgs boson using diphoton events produced in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV is performed using data corresponding to an integrated luminosity of 4.9/fb collected by the ATLAS experiment at the Large Hadron Collider. A specific benchmark model is considered where all the fermion couplings to the Higgs boson are set to zero and the bosonic couplings are kept at the Standard Model values (fermiophobic Higgs model). The largest excess with respect to the background-only hypothesis is found at 125.5 GeV, with a local significance of 2.9 standard deviations, which reduces to 1.6 standard deviations when taking into account the look-elsewhere effect. The data exclude the fermiophobic Higgs model in the ranges 110.0 - 118.0 GeV and 119.5 - 121.0 GeV at 95% confidence level..
542. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC, Phys. Lett. B, 10.1016/j.physletb.2012.08.020, 716, 1-29, 2012.09, A search for the Standard Model Higgs boson in proton-proton collisions with the ATLAS detector at the LHC is presented. The datasets used correspond to integrated luminosities of approximately 4.8 fb^-1 collected at sqrt(s) = 7 TeV in 2011 and 5.8 fb^-1 at sqrt(s) = 8 TeV in 2012. Individual searches in the channels H->ZZ^(*)->llll, H->gamma gamma and H->WW->e nu mu nu in the 8 TeV data are combined with previously published results of searches for H->ZZ^(*), WW^(*), bbbar and tau^+tau^- in the 7 TeV data and results from improved analyses of the H->ZZ^(*)->llll and H->gamma gamma channels in the 7 TeV data. Clear evidence for the production of a neutral boson with a measured mass of 126.0 +/- 0.4(stat) +/- 0.4(sys) GeV is presented. This observation, which has a significance of 5.9 standard deviations, corresponding to a background fluctuation probability of 1.7x10^-9, is compatible with the production and decay of the Standard Model Higgs boson..
543. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A search for ttbar resonances in lepton+jets events with highly boosted top quarks collected in pp collisions at √s = 7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP09(2012)041, 2012, 09, 041, 2012.09, A search for resonant production of high-mass top-quark pairs is performed on 2.05 fb^-1 of proton-proton collisions at sqrt(s) = 7 TeV collected in 2011 with the ATLAS experiment at the Large Hadron Collider. This analysis of the lepton+jets final state is specifically designed for the particular topology that arises from the decay of highly boosted top quarks. The observed ttbar invariant mass spectrum is found to be compatible with the Standard Model prediction and 95% credibility level upper limits are derived on the ttbar production rate through new massive states. An upper limit of 0.7 pb is set on the production cross section times branching fraction of a narrow 1 TeV resonance. A Kaluza-Klein gluon with a mass smaller than 1.5 TeV is excluded. .
544. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Standard Model Higgs boson in the H to tau+ tau- decay mode in √s = 7 TeV pp collisions with ATLAS, JHEP, 10.1007/JHEP09(2012)070, 2012, 09, 070, 2012.09, A search for the Standard Model Higgs boson decaying into a pair of tau leptons is reported. The analysis is based on a data sample of proton-proton collisions collected by the ATLAS experiment at the LHC and corresponding to an integrated luminosity of 4.7 fb^-1. No significant excess over the expected background is observed in the Higgs boson mass range of 100-150 GeV. The observed (expected) upper limits on the cross section times the branching ratio for H to tau+ tau- are found to be between 2.9 (3.4) and 11.7 (8.2) times the Standard Model prediction for this mass range. .
545. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for scalar top quark pair production in natural gauge mediated supersymmetry models with the ATLAS detector in pp collisions at root s=7 TeV, PHYSICS LETTERS B, 10.1016/j.physletb.2012.07.010, 715, 1-3, 44-60, 2012.08.
546. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Pair Production of a New b ' Quark that Decays into a Z Boson and a Bottom Quark with the ATLAS Detector, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.109.071801, 109, 7, 2012.08.
547. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for events with large missing transverse momentum, jets, and at least two tau leptons in 7 TeV proton-proton collision data with the ATLAS detector ATLAS Collaboration, PHYSICS LETTERS B, 10.1016/j.physletb.2012.06.055, 714, 2-5, 180-196, 2012.08.
548. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for tb Resonances in Proton-Proton Collisions at root s=7 TeV with the ATLAS Detector, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.109.081801, 109, 8, 2012.08.
549. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Combined search for the Standard Model Higgs boson in pp collisions at root s=7 TeV with the ATLAS detector, PHYSICAL REVIEW D, 10.1103/PhysRevD.86.032003, 86, 3, 2012.08.
550. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for supersymmetry with jets, missing transverse momentum and at least one hadronically decaying tau lepton in proton-proton collisions at root s=7 TeV with the ATLAS detector ATLAS Collaboration, PHYSICS LETTERS B, 10.1016/j.physletb.2012.06.061, 714, 2-5, 197-214, 2012.08.
551. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Combined search for the Standard Model Higgs boson in pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.86.032003, 86, 032003, 2012.08, A combined search for the Standard Model Higgs boson with the ATLAS detector at the LHC is presented. The datasets used correspond to integrated luminosities from 4.6 fb^-1 to 4.9 fb^-1 of proton-proton collisions collected at sqrt(s) = 7 TeV in 2011. The Higgs boson mass ranges of 111.4 GeV to 116.6 GeV, 119.4 GeV to 122.1 GeV, and 129.2 GeV to 541 GeV are excluded at the 95% confidence level, while the range 120 GeV to 560 GeV is expected to be excluded in the absence of a signal. An excess of events is observed at Higgs boson mass hypotheses around 126 GeV with a local significance of 2.9 standard deviations (sigma). The global probability for the background to produce an excess at least as significant anywhere in the entire explored Higgs boson mass range of 110-600 GeV is estimated to be ~15%, corresponding to a significance of approximately one sigma. .
552. G. Abbiendi, K. Kawagoe et al. (The ALEPH, DELPHI, L3, and OPAL Collaborations), Search for charged Higgs bosons in e(+)e(-) collisions at root s=189-209 GeV, EUROPEAN PHYSICAL JOURNAL C, 10.1140/epjc/s10052-012-2076-0, 72, 7, 2012.07.
553. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Forward-backward correlations and charged-particle azimuthal distributions in pp interactions using the ATLAS detector, JOURNAL OF HIGH ENERGY PHYSICS, 10.1007/JHEP07(2012)019, 7, 2012.07.
554. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Hunt for new phenomena using large jet multiplicities and missing transverse momentum with ATLAS in 4.7fb(-1) of root s=7 TeV proton-proton collisions, JOURNAL OF HIGH ENERGY PHYSICS, 10.1007/JHEP07(2012)167, 7, 2012.07.
555. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Determination of the Strange-Quark Density of the Proton from ATLAS Measurements of the W -> lv and Z -> ll Cross Sections, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.109.012001, 109, 1, 2012.07.
556. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Down-Type Fourth Generation Quarks with the ATLAS Detector in Events with One Lepton and Hadronically Decaying W Bosons, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.109.032001, 109, 3, 2012.07.
557. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A search for t (t)over-bar resonances with the ATLAS detector in 2.05 fb(-1) of proton-proton collisions at root s=7 TeV, EUROPEAN PHYSICAL JOURNAL C, 10.1140/epjc/s10052-012-2083-1, 72, 7, 2012.07.
558. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of inclusive jet and dijet production in pp collisions at root s=7 TeV using the ATLAS detector, PHYSICAL REVIEW D, 10.1103/PhysRevD.86.014022, 86, 1, 2012.07.
559. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the azimuthal anisotropy for charged particle production in root s(NN)=2.76 TeV lead-lead collisions with the ATLAS detector, PHYSICAL REVIEW C, 10.1103/PhysRevC.86.014907, 86, 1, 2012.07.
560. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for heavy neutrinos and right-handed W bosons in events with two leptons and jets in pp collisions at root s=7 TeV with the ATLAS detector, EUROPEAN PHYSICAL JOURNAL C, 10.1140/epjc/s10052-012-2056-4, 72, 7, 2012.07.
561. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of tau polarization in W -> tau nu decays with the ATLAS detector in pp collisions at root s=7 TeV, EUROPEAN PHYSICAL JOURNAL C, 10.1140/epjc/s10052-012-2062-6, 72, 7, 2012.07.
562. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for pair-produced heavy quarks decaying to Wq in the two-lepton channel at root(s)=7 TeV with the ATLAS detector, PHYSICAL REVIEW D, 10.1103/PhysRevD.86.012007, 86, 1, 2012.07.
563. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the decay B-s(0) -> mu(+)mu(-) with the ATLAS detector, PHYSICS LETTERS B, 10.1016/j.physletb.2012.06.013, 713, 4-5, 387-407, 2012.07.
564. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A search for ttbar resonances with the ATLAS detector in 2.05 fb-1 of proton-proton collisions at √s = 7 TeV, Eur. Phys. J. C, 10.1140/epjc/s10052-012-2083-1, 72, 2083, 2012.07, A search for top quark pair resonances in final states containing at least one electron or muon has been performed with the ATLAS experiment at the CERN Large Hadron Collider. The search uses a data sample corresponding to an integrated luminosity of 2.05 fb^-1, which was recorded in 2011 at a proton-proton centre-of-mass energy of 7 TeV. No evidence for a resonance is found and limits are set on the production cross-section times branching ratio to ttbar for narrow and wide resonances. For narrow Z' bosons, the observed 95% credibility level limits range from 9.3 pb to 0.95 pb for masses in the range of m_Z' = 500 GeV to m_Z' = 1300 GeV. The corresponding excluded mass region for a leptophobic topcolour Z' boson (Kaluza-Klein gluon excitation in the Randall-Sundrum model) is m_Z' < 880 GeV (m_{g_KK} < 1130 GeV)..
565. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for resonant WZ production in the WZ -> lvl ' l ' channel in root(s)=7 TeV pp collisions with the ATLAS detector, PHYSICAL REVIEW D, 10.1103/PhysRevD.85.112012, 85, 11, 2012.06.
566. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for charged Higgs bosons decaying via H-+/- -> tau nu in t(t)over-bar events using pp collision data at root s=7 TeV with the ATLAS detector, JOURNAL OF HIGH ENERGY PHYSICS, 10.1007/JHEP06(2012)039, 6, 2012.06.
567. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Gluinos in Events with Two Same-Sign Leptons, Jets, and Missing Transverse Momentum with the ATLAS Detector in pp Collisions at root s=7 TeV, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.108.241802, 108, 24, 2012.06.
568. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for lepton flavour violation in the e mu continuum with the ATLAS detector in root s=7 TeV pp collisions at the LHC, EUROPEAN PHYSICAL JOURNAL C, 10.1140/epjc/s10052-012-2040-z, 72, 6, 2012.06.
569. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Supersymmetry in Events with Three Leptons and Missing Transverse Momentum in root s=7 TeV pp Collisions with the ATLAS Detector, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.108.261804, 108, 26, 2012.06.
570. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the top quark mass with the template method in the t(t)over-bar -> lepton plus jets channel using ATLAS data, EUROPEAN PHYSICAL JOURNAL C, 10.1140/epjc/s10052-012-2046-6, 72, 6, 2012.06.
571. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new particles decaying to ZZ using final states with leptons and jets with the ATLAS detector in root s=7 TeV proton-proton collisions, PHYSICS LETTERS B, 10.1016/j.physletb.2012.05.020, 712, 4-5, 331-350, 2012.06.
572. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Pair Production of a Heavy Up-Type Quark Decaying to a W Boson and a b Quark in the lepton plus jets Channel with the ATLAS Detector, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.108.261802, 108, 26, 2012.06.
573. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of t(t)over-bar production with a veto on additional central jet activity in pp collisions at root s=7 TeV using the ATLAS detector, EUROPEAN PHYSICAL JOURNAL C, 10.1140/epjc/s10052-012-2043-9, 72, 6, 2012.06.
574. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the W boson polarization in top quark decays with the ATLAS detector, JOURNAL OF HIGH ENERGY PHYSICS, 10.1007/JHEP06(2012)088, 6, 2012.06.
575. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for supersymmetry in pp collisions at root s=7 Te V in final states with missing transverse momentum and b-jets with the ATLAS detector, PHYSICAL REVIEW D, 10.1103/PhysRevD.85.112006, 85, 11, 2012.06.
576. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the W W cross section in root s=7 TeV pp collisions with the ATLAS detector and limits on anomalous gauge couplings, PHYSICS LETTERS B, 10.1016/j.physletb.2012.05.003, 712, 4-5, 289-308, 2012.06.
577. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the charge asymmetry in top quark pair production in pp collisions at root s=7 TeV using the ATLAS detector, EUROPEAN PHYSICAL JOURNAL C, 10.1140/epjc/s10052-012-2039-5, 72, 6, 2012.06.
578. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a Light Higgs Boson Decaying to Long-Lived Weakly Interacting Particles in Proton-Proton Collisions at root s=7 TeV with the ATLAS Detector, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.108.251801, 108, 25, 2012.06.
579. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for FCNC single top-quark production at root s=7 TeV with the ATLAS detector, PHYSICS LETTERS B, 10.1016/j.physletb.2012.05.022, 712, 4-5, 351-369, 2012.06.
580. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of W boson polarization in top quark decays with the ATLAS detector, JHEP, 10.1007/JHEP06(2012)088, 2012, 06, 088, 2012.06, This paper presents measurements of the polarization of W bosons in top quark decays, derived from ttbar events with missing transverse momentum, one charged lepton and at least four jets, or two charged leptons and at least two jets. Data from pp collisions at a centre-of-mass energy of 7 TeV were collected with the ATLAS experiment at the LHC and correspond to an integrated luminosity of 1.04 fb^-1. The measured fractions of longitudinally, left- and right-handed polarization are F_0=0.67+/-0.07, F_L=0.32+/-0.04 and F_R=0.01+/-0.05, in agreement with the Standard Model predictions. As the polarization of the W bosons in top quark decays is sensitive to the Wtb vertex Lorentz structure and couplings, the measurements were used to set limits on anomalous contributions to the Wtb couplings..
581. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the production cross section of an isolated photon associated with jets in proton-proton collisions at root s=7 TeV with the ATLAS detector, PHYSICAL REVIEW D, 10.1103/PhysRevD.85.092014, 85, 9, 2012.05.
582. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for heavy vector-like quarks coupling to light quarks in proton-proton collisions at root s=7 TeV with the ATLAS detector, PHYSICS LETTERS B, 10.1016/j.physletb.2012.03.082, 712, 1-2, 22-39, 2012.05.
583. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for contact interactions in dilepton events from pp collisions at root s=7 TeV with the ATLAS detector, PHYSICS LETTERS B, 10.1016/j.physletb.2012.04.026, 712, 1-2, 40-58, 2012.05.
584. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Scalar Bottom Quark Pair Production with the ATLAS Detector in pp Collisions at root s=7 TeV, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.108.181802, 108, 18, 2012.05.
585. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at root s=7 TeV with the ATLAS experiment, EUROPEAN PHYSICAL JOURNAL C, 10.1140/epjc/s10052-012-2001-6, 72, 5, 2012.05.
586. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the cross section for top-quark pair production in pp collisions at root s=7 TeV with the ATLAS detector using final states with two high-p(T) leptons, JOURNAL OF HIGH ENERGY PHYSICS, 10.1007/JHEP05(2012)059, 5, 2012.05.
587. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Observation of Spin Correlation in t(t)over-bar Events from pp Collisions at root s=7 TeV Using the ATLAS Detector, PHYSICS LETTERS B, 10.1103/PhysRevLett.108.212001, 108, 21, 2012.05.
588. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the top quark pair production cross-section with ATLAS in the single lepton channel, PHYSICS LETTERS B, 10.1016/j.physletb.2012.03.083, 711, 3-4, 244-263, 2012.05.
589. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Study of jets produced in association with a W boson in pp collisions at root s=7 TeV with the ATLAS detector, PHYSICAL REVIEW D, 10.1103/PhysRevD.85.092002, 85, 9, 2012.05.
590. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Jet mass and substructure of inclusive jets in root s=7 TeV pp collisions with the ATLAS experiment, JOURNAL OF HIGH ENERGY PHYSICS, 10.1007/JHEP05(2012)128, 5, 2012.05.
591. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Production of Resonant States in the Photon-Jet Mass Distribution Using pp Collisions at root s=7 TeV Collected by the ATLAS Detector, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.108.211802, 108, 21, 2012.05.
592. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of inclusive two-particle angular correlations in pp collisions with the ATLAS detector at the LHC, JOURNAL OF HIGH ENERGY PHYSICS, 10.1007/JHEP05(2012)157, 5, 2012.05.
593. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Standard Model Higgs boson in the decay channel H->ZZ(*)->4l with 4.8 fb-1 of pp collision data at sqrt(s) = 7 TeV with ATLAS., Phys. Lett. B, 10.1016/j.physletb.2012.03.005, 710, 3, 383-402, 2012.04.
594. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Observation of a new χb state in radiative transitions to Υ(1S) and Υ(2S) at ATLAS., Phys. Rev. Lett., 10.1103/PhysRevLett.108.152001, 108, 15, 152001, 2012.04.
595. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Extra Dimensions using diphoton events in 7 TeV proton-proton collisions with the ATLAS detector., Phys. Lett. B, 10.1016/j.physletb.2012.03.022, 710, 4-5, 538-556, 2012.04.
596. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Diphoton Events with Large Missing Transverse Momentum in 1 fb^-1 of 7 TeV Proton-Proton Collision Data with the ATLAS Detector., Phys. Lett. B, 10.1016/j.physletb.2012.02.054, 710, 4-5, 519-537, 2012.04.
597. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for excited leptons in proton-proton collisions at root s=7 TeV with the ATLAS detector, PHYSICAL REVIEW D, 10.1103/PhysRevD.85.072003, 85, 7, 2012.04.
598. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for same-sign top-quark production and fourth-generation down-type quarks in pp collisions at root s=7 TeV with the ATLAS detector, JOURNAL OF HIGH ENERGY PHYSICS, 10.1007/JHEP04(2012)069, 4, 2012.04.
599. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for decays of stopped, long-lived particles from 7 TeV pp collisions with the ATLAS detector, EUROPEAN PHYSICAL JOURNAL C, 10.1140/epjc/s10052-012-1965-6, 72, 4, 2012.04.
600. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the centrality dependence of the charged particle pseudorapidity distribution in lead-lead collisions at root s(NN)=2.76 TeV with the ATLAS detector, PHYSICS LETTERS B, 10.1016/j.physletb.2012.02.045, 710, 3, 363-382, 2012.04.
601. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the inclusive W-+/- and Z/gamma* cross sections in the e and mu decay channels in pp collisions at root s=7 TeV with the ATLAS detector, PHYSICAL REVIEW D, 10.1103/PhysRevD.85.072004, 85, 7, 2012.04.
602. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for anomaly-mediated supersymmetry breaking with the ATLAS detector based on a disappearing-track signature in pp collisions at root s=7 TeV, EUROPEAN PHYSICAL JOURNAL C, 10.1140/epjc/s10052-012-1993-2, 72, 4, 2012.04.
603. KIYOTOMO KAWAGOE, Construction and performance of a silicon photomultiplier/extruded scintillator tail-catcher and muon-tracker, JOURNAL OF INSTRUMENTATION, 10.1088/1748-0221/7/04/P04015, 7, 2012.04.
604. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Electron performance measurements with the ATLAS detector using the 2010 LHC proton-proton collision data, Eur. Phys. J. C, 10.1140/epjc/s10052-012-1909-1, 72.0, 3.0, 1909.0, 2012.03.
605. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in √s =7 TeV proton-proton collisions, Phys. Lett. B, 10.1016/j.physletb.2012.02.051, 710.0, 1.0, 67-85, 2012.03, 2011年に収集した重心系エネルギー7TeV、積分ルミノシティ1.04fb-1の陽子陽子衝突データを用いて、大きな横運動量欠損とジェットを持つ事象により、グルイーノとスカラークォークの探索を行った。その結果、標準模型の予測を超える事象は観測されず、それらの質量についてそれぞれ700GeV, 875GeVの下限がついた。.
606. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Searches for supersymmetry with the ATLAS detector using final states with two leptons and missing transverse momentum in √s = 7 TeV proton-proton collisions, Phys. Lett. B, 10.1016/j.physletb.2012.01.076, 709.0, 3.0, 137-157, 2012.03, 2011年に収集した重心系エネルギー7TeV、積分ルミノシティ1.04fb-1の陽子陽子衝突データを用いて、大きな横運動量欠損、ジェット、および孤立したレプトンを持つ事象により、超対称性粒子の探索を行った。その結果、標準模型の予測を超える事象は観測されず、生成断面積に制限を付け、超重力モデルの元で超対称性パラメータに制限を付けた。.
607. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for strong gravity signatures in same-sign dimuon final states using the ATLAS detector at the LHC, Phys. Lett. B, 10.1016/j.physletb.2012.02.049, 709.0, 4-5, 322-340, 2012.03, 重心系エネルギー7TeVの陽子陽子衝突実験で微視的ブラックホールが同符号のミュウ粒子に崩壊する事象を探索を行った。その結果は、標準模型の予測とあっており、低スケールの重力模型に制限を付けた。.
608. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the WZ production cross section and limits on anomalous triple gauge couplings in proton-proton collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2012.02.053, 709.0, 4-5, 341-357, 2012.03, 重心系エネルギー7TeV、積分ルミノシティ1.02fb-1の陽子陽子衝突データを用いて、WZ生成の断面積を測定した。また、その測定から、異常な三重ゲージ結合に対する制限を付けた。.
609. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of D*+/- meson production in jets from pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.85.052005, 85.0, 5.0, 052005, 2012.03, 重心系エネルギー7TeVの陽子陽子衝突実験で荷電D*中間子生成の測定を行った。ジェットの中の荷電D*中間子の運動量比が小さいところは、モンテカルロシミュレーションがうまく記述できないことがわかった。.
610. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for first generation scalar leptoquarks in pp collisions at sqrt{s}=7 TeV with the ATLAS detector., Phys. Lett. B, 10.1016/j.physletb.2012.02.004, 709, 3, 158-176, 2012.03.
611. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Higgs boson in the H -> WW(*) -> l nu l nu decay channel in pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.108.111802, 108.0, 11.0, 111802, 2012.03, 重心系エネルギー7TeV、積分ルミノシティ2.05fb-1の陽子陽子衝突データを用いて、ヒッグス粒子がW粒子対に崩壊し、さらに2個のレプトンと2個のニュートリノに崩壊するチャンネルの探索を行った。有意に過剰な事象は観測されず、110-300GeVの質量領域でヒッグス粒子の生成断面積に制限を付けた。145-206GeVの標準模型ヒッグス粒子の存在を棄却した。.
612. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Higgs boson in the H->WW(*)->lvlv decay channel in pp collisions at sqrt{s} = 7 TeV with the ATLAS detector., Phys. Rev. Lett., 10.1103/PhysRevLett.108.111802, 108, 11, 111802, 2012.03.
613. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Rapidity gap cross sections measured with the ATLAS detector in pp collisions at √s = 7 TeV, Eur. Phys. J. C, 10.1140/epjc/s10052-012-1926-0, 72.0, 3.0, 1926, 2012.03.
614. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Combined search for the Standard Model Higgs boson using up to 4.9 fb-1 of pp collision data at √s = 7 TeV with the ATLAS detector at the LHC, Phys. Lett. B, 10.1016/j.physletb.2012.02.044, 710.0, 1.0, 49-66, 2012.03, ヒッグス粒子の崩壊チャンネルを組み合わせた探索を行った。重心系エネルギー7TeVの陽子陽子衝突で積分ルミノシティ1.04fb-1から4.9fb-1のデータを解析し、112.9-115.5GeV, 131-238GeV, 251-466GeVの質量領域で標準模型ヒッグス粒子を信頼度95%で棄却した。ヒッグスの質量126GeV付近に過剰な事象があり、3.5σの有意度であった。.
615. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Standard Model Higgs boson in the diphoton decay channel with 4.9 fb-1 of pp collisions at √s =7 TeV with ATLAS, Phys. Rev. Lett., 10.1103/PhysRevLett.108.111803, 108.0, 11.0, 111803, 2012.03, ヒッグス粒子が2光子に崩壊するチャンネルの探索を行った。重心系エネルギー7TeV、4.9fb-1の陽子陽子衝突実験データを解析したところ、質量110-150GeVの範囲で、ヒッグス粒子が存在しない場合に対して126.5GeVの所に最大2.8σの過剰が観測された。113–115 GeV と 134.5–136 GeVの領域の標準模型ヒッグス粒子の存在は信頼度95%で否定された。.
616. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in √s=7 TeV proton-proton collisions, Phys. Lett. B, 10.1016/j.physletb.2012.02.051, 710, 1, 67-85, 2012.03, LHC/ATLAS実験による超対称性粒子の探索。.
617. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Standard Model Higgs boson in the diphoton decay channel with 4.9 fb-1 of pp collisions at √s =7 TeV with ATLAS, Phys. Rev. Lett., 10.1103/PhysRevLett.108.111803, 108, 11, 111803, 2012.03, ヒッグス粒子が2光子に崩壊するチャンネルの探索を行った。重心系エネルギー7TeV、4.9fb-1の陽子陽子衝突実験データを解析したところ、質量110-150GeVの範囲で、ヒッグス粒子が存在しない場合に対して126.5GeVの所に最大2.8σの過剰が観測された。113–115 GeV と 134.5–136 GeVの領域の標準模型ヒッグス粒子の存在は信頼度95%で否定された。.
618. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Combined search for the Standard Model Higgs boson using up to 4.9 fb-1 of pp collision data at √s = 7 TeV with the ATLAS detector at the LHC, Phys. Lett. B, 10.1016/j.physletb.2012.02.044, 710, 1, 49-66, 2012.03, ヒッグス粒子の崩壊チャンネルを組み合わせた探索を行った。重心系エネルギー7TeVの陽子陽子衝突で積分ルミノシティ1.04fb-1から4.9fb-1のデータを解析し、112.9-115.5GeV, 131-238GeV, 251-466GeVの質量領域で標準模型ヒッグス粒子を信頼度95%で棄却した。ヒッグスの質量126GeV付近に過剰な事象があり、3.5σの有意度であった。.
619. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for first generation scalar leptoquarks in pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2012.02.004, 709, 3, 158-176, 2012.03, 重心系エネルギー7TeVで積分ルミノシティ1.03fb-1の陽子陽子衝突データを用いて、第1世代レプトクォークの探索を行った。その結果、レプトクォークから荷電レプトンへの崩壊分岐比が1.0(0.5)の場合、質量の下限値として660(607)GeVを得た。.
620. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of D*+/- meson production in jets from pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.85.052005, 85, 5, 052005, 2012.03, 重心系エネルギー7TeVの陽子陽子衝突実験で荷電D*中間子生成の測定を行った。ジェットの中の荷電D*中間子の運動量比が小さいところは、モンテカルロシミュレーションがうまく記述できないことがわかった。.
621. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Higgs boson in the H -> WW(*) -> l nu l nu decay channel in pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.108.111802, 108, 11, 111802, 2012.03, 重心系エネルギー7TeV、積分ルミノシティ2.05fb-1の陽子陽子衝突データを用いて、ヒッグス粒子がW粒子対に崩壊し、さらに2個のレプトンと2個のニュートリノに崩壊するチャンネルの探索を行った。有意に過剰な事象は観測されず、110-300GeVの質量領域でヒッグス粒子の生成断面積に制限を付けた。145-206GeVの標準模型ヒッグス粒子の存在を棄却した。.
622. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the WZ production cross section and limits on anomalous triple gauge couplings in proton-proton collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2012.02.053, 709, 4-5, 341-357, 2012.03, 重心系エネルギー7TeV、積分ルミノシティ1.02fb-1の陽子陽子衝突データを用いて、WZ生成の断面積を測定した。また、その測定から、異常な三重ゲージ結合に対する制限を付けた。.
623. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for strong gravity signatures in same-sign dimuon final states using the ATLAS detector at the LHC, Phys. Lett. B, 10.1016/j.physletb.2012.02.049, 709, 4-5, 322-340, 2012.03, 重心系エネルギー7TeVの陽子陽子衝突実験で微視的ブラックホールが同符号のミュウ粒子に崩壊する事象を探索を行った。その結果は、標準模型の予測とあっており、低スケールの重力模型に制限を付けた。.
624. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Searches for supersymmetry with the ATLAS detector using final states with two leptons and missing transverse momentum in √s = 7 TeV proton-proton collisions, Phys. Lett. B, 10.1016/j.physletb.2012.01.076, 709, 3, 137-157, 2012.03, 2011年に収集した重心系エネルギー7TeV、積分ルミノシティ1.04fb-1の陽子陽子衝突データを用いて、大きな横運動量欠損、ジェット、および孤立したレプトンを持つ事象により、超対称性粒子の探索を行った。その結果、標準模型の予測を超える事象は観測されず、生成断面積に制限を付け、超重力モデルの元で超対称性パラメータに制限を付けた。.
625. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in √s =7 TeV proton-proton collisions, Phys. Lett. B, 10.1016/j.physletb.2012.02.051, 710, 1, 67-85, 2012.03, 2011年に収集した重心系エネルギー7TeV、積分ルミノシティ1.04fb-1の陽子陽子衝突データを用いて、大きな横運動量欠損とジェットを持つ事象により、グルイーノとスカラークォークの探索を行った。その結果、標準模型の予測を超える事象は観測されず、それらの質量についてそれぞれ700GeV, 875GeVの下限がついた。.
626. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the top quark pair production cross section in pp collisions at √s = 7 TeV in dilepton final states with ATLAS, Phys. Lett. B, 10.1016/j.physletb.2011.12.055, 707.0, 5.0, 459-477, 2012.02, LHC のアトラス検出器で収集した、重心系エネルギー 7 TeV での陽子-陽子衝突におけるトップクォーク対の生成断面積の測定について報告する。大きな消失横運動量と2個以上のジェットを伴い、2個のレプトンを含む事象を選別した。積分ルミノシティ 35 pb-1 を用い、172.5 GeV のトップクォーク質量を過程して、171 +/- 20(統計) +/- 14(系統) +8-6(ルミノシティ) pb の断面積を測定した。少なくとも1個のジェットが b クォーク起源と同定されたことを要求する測定では、前記の断面積と無矛盾な結果であり、2個のレプトンを含む事象が b クォークジェットを伴っていることを示した。これらの測定は、標準模型の予想と良く一致している。.
627. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A measurement of the ratio of the W and Z cross sections with exactly one associated jet in pp collisions at √s = 7 TeV with ATLAS, Phys. Lett. B, 10.1016/j.physletb.2012.01.042, 708.0, 3-5, 221-240, 2012.02, 1個のジェットを伴うW ボソンと Z ボソンの生成断面積比を、ジェットの横運動量しきい値の関数として発表する。実験的理論的不定性が最大限キャンセルする方法で測定し、検出器アクセプタンスに対応する粒子レベルで、また、総断面積比として報告する。結果は、重心系エネルギー 7 TeVでの LHC における pp 衝突でアトラス検出器で収集され、積分ルミノシティ 33 pb-1 を用いて得られ、QCD の主要項、主要 log、主要項の次の次数での予想と比較し、実験的理論的不定性の範囲で一致した。比は、横運動量 30 GeV 以上の1個のジェットを伴う事象で、電子チャンネルで 8.73 +/- 0.30 (統計) +/- 0.40 (系統)、ミューオンチャンネルで 8.49 +/- 0.23 (統計) +/- 0.33 (系統) であった。.
628. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the pseudorapidity and transverse momentum dependence of the elliptic flow of charged particles in lead-lead collisions at √sNN = 2.76 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2011.12.056, 707.0, 3-4, 330-348, 2012.02, LHC におけるアトラス検出器を用いた、核子あたりの重心系エネルギー 2.76 TeV、積分ルミノシティ約 7 ub-1 での鉛-鉛衝突における、荷電粒子の楕円型フローの測定について記述する。楕円型フローの測定は、擬ラピディティ 2.5 以下、横運動量 0.5 - 20 GeV の範囲で、楕円型フローの測定を行い、変数 v_2 は、前方カロリメータを用いて測定された事象平面と各飛跡の相関から得られた。横運動量約 3 GeV で最大に達して減少し、7 - 8 GeV 以上で依存性が弱くなる。測定された擬ラピディティの範囲で、v_2 は衝突中心度と粒子横運動量に関しては擬ラピディティに近似的に独立であった。最近の LHC からの結果と同様に、以前になされたより低い衝突エネルギーでの測定との関係を議論する。.
629. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for New Physics in the Dijet Mass Distribution using 1 fb-1 of pp Collision Data at √s = 7 TeV collected by the ATLAS Detector, Phys. Lett. B, 10.1016/j.physletb.2012.01.035, 708.0, 1-2, 37-54, 2012.02, 2011年にアトラス実験で収集した重心系エネルギー 7 TeV、積分ルミノシティ 1.0 fb-1 での LHC における陽子-陽子衝突で生成されたジェット対の不変質量分布についての研究を報告する。約 4 TeV までのジェット対質量がデータで見られ、背景事象を超える共鳴状態の生成の証拠はなかった。数々の新物理仮説に関して、95% CL での制限を付した:励起されたクォークは 2.99 TeV 以下の質量を排除、アクシグルーオンは 3.32 TeV 以下の質量を排除、カラー8重項スカラー共鳴は 1.92 TeV 以下の質量を排除した。.
630. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of the electron and muon inclusive cross-sections in proton-proton collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2011.12.054, 707.0, 5.0, 438-458, 2012.02, 重心系エネルギー 7 TeV での陽子-陽子衝突における包含的な電子とミューオン生成の微分断面積について発表する。データは LHC のアトラス検出器で収集され、ミューオンの断面積は、4 - 100 GeV の横運動量、擬ラピディティ 2.5 以下で、横運動量の関数として測定した。また、電子とミューオンの断面積は、7 - 26 GeV の横運動量、擬ラピディティ 2.0 以下 (1.37 - 1.52 を除く)で測定した。積分ルミノシティは、1.3 pb-1 (電子)、1.4 pb-1 (ミューオン) であった。W/Z/gamma* の寄与を差し引き後、微分断面積は、NLL 高 pT resummaion を用いた固定次 NLO 計算から得られる重いフレーバー生成に関する理論予想と良く一致し、その NLL resummation の効果に感度があることが示された。.
631. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the cross section for the production of a W boson in association with b-jets in pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2011.12.046, 707.0, 5.0, 418-437, 2012.02, 重心系エネルギー 7 TeV、積分ルミノシティ 35 pb-1 における、 pp 衝突からの 1個または2個のジェット (その内少なくとも1個は b ジェット) を伴う W ボソンの生成断面積について発表する。トップの崩壊に起因する生成は含まれていない。W + b ジェット断面積は、横運動量 25 GeV 以上でラピディティ +/- 2.1 以内の反 kt クラスタリングアルゴリズムで再構成されたジェットで定義され、b ジェットは、二次崩壊点を再構成して同定された。基準となる断面積は、電子とミューオンに崩壊する W ボソンについて測定され、一つのレプトンフレーバーについて 10.2 +/- 1.9 (統計) +/- 2.6 (系統) pb であった。主要項の次の次数での摂動論的量子色力学の予想は、測定値と無矛盾だが、より小さい値という結果であった。.
632. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS, Phys. Lett. B, 10.1016/j.physletb.2011.12.057, 707.0, 5.0, 478-496, 2012.02, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ33pb-1の陽子陽子衝突データを用いて、重い新粒子の崩壊により衝突点からずれたバーテックスを作る事象の探索を行った。そのような事象は標準模型を超える様々な理論で予言されるが、そのような信号は得られず、それらの理論に制限を付けた。.
633. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the production cross section for Z/gamma* in association with jets in pp collisions at √s = 7 TeV with the ATLAS Detector, Phys. Rev. D, 10.1103/PhysRevD.85.032009, 85.0, 3.0, 032009, 2012.02, 2010年に収集した重心系エネルギー7TeVのデータを用いて、ジェットを伴うZ/γ*粒子生成の測定を行った。この解析では、Z/γ*粒子が電子対またはミュー粒子対に崩壊するチャンネルを使っている。その測定結果を、NLO摂動QCDの予測と比較した。.
634. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for anomalous production of prompt like-sign muon pairs and constraints on physics beyond the Standard Model with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.85.032004, 85.0, 3.0, 032004, 2012.02, 重心系エネルギー7TeVで積分ルミノシティ1.6fb-1の陽子陽子衝突データを用いて、同符号のミュー粒子対を持つ事象の異常生成を探索した。その結果は、標準模型の予測と矛盾がなく、その不変質量分布にピークがないことから、電荷2を持つヒッグス粒子など標準模型を超える物理に対する制限を付けた。.
635. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for anomalous production of prompt like-sign muon pairs and constraints on physics beyond the Standard Model with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.85.032004, 85, 3, 032004, 2012.02, 重心系エネルギー7TeVで積分ルミノシティ1.6fb-1の陽子陽子衝突データを用いて、同符号のミュー粒子対を持つ事象の異常生成を探索した。その結果は、標準模型の予測と矛盾がなく、その不変質量分布にピークがないことから、電荷2を持つヒッグス粒子など標準模型を超える物理に対する制限を付けた。.
636. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the production cross section for Z/gamma* in association with jets in pp collisions at √s = 7 TeV with the ATLAS Detector, Phys. Rev. D, 10.1103/PhysRevD.85.032009, 85, 3, 032009, 2012.02, 2010年に収集した重心系エネルギー7TeVのデータを用いて、ジェットを伴うZ/γ*粒子生成の測定を行った。この解析では、Z/γ*粒子が電子対またはミュー粒子対に崩壊するチャンネルを使っている。その測定結果を、NLO摂動QCDの予測と比較した。.
637. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS, Phys. Lett. B, 10.1016/j.physletb.2011.12.057, 707, 5, 478-496, 2012.02, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ33pb-1の陽子陽子衝突データを用いて、重い新粒子の崩壊により衝突点からずれたバーテックスを作る事象の探索を行った。そのような事象は標準模型を超える様々な理論で予言されるが、そのような信号は得られず、それらの理論に制限を付けた。.
638. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Performance of missing transverse momentum reconstruction in proton-proton collisions at 7 TeV with ATLAS, Eur. Phys. J. C, 10.1140/epjc/s10052-011-1844-6, 72.0, 1.0, 1844.0, 2012.01.
639. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Performance of the ATLAS Trigger System in 2010, Eur. Phys. J. C, 10.1140/epjc/s10052-011-1849-1, 72.0, 1.0, 1849.0, 2012.01.
640. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), A measurement of the material in the ATLAS inner detector using secondary hadronic interactions, JINST, 10.1088/1748-0221/7/01/P01013, 7.0, P01013, 2012.01.
641. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of isolated diphoton cross-section in pp collision at √s = 7 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.85.012003, 85.0, 1.0, 012003, 2012.01, アトラス実験は、重心系エネルギー 7 TeV での陽子-陽子衝突において、終状態に2個の孤立光子を持つ事象の生成断面積を測定した。2010年に得られたフルデータセットを用い、積分ルミノシティは 37 pb-1 に相当する。背景事象は、ハドロンジェットと孤立電子から構成され、データを用いた手法と差分法により評価された。微分断面積を、光子対質量、総横運動量、方位角分離の関数として示し、主要項の次の次数での QCD の予想と比較する。.
642. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the W to tau nu Cross Section in pp Collisions at √s = 7 TeV with the ATLAS experiment, Phys. Lett. B, 10.1016/j.physletb.2011.11.057, 706.0, 4-5, 276-294, 2012.01, 2010年の重心系エネルギー 7 TeV での陽子-陽子衝突において、LHC のアトラス検出器で収集した 積分ルミノシティ 34 pb-1 のデータを用い、タウとニュートリノに崩壊する W ボソンの生成断面積を測定した。高い検出器アクセプタンスの領域で測定を行い、フルの位相空間へ外挿し、総断面積と崩壊比の積は 11.1 +/- 0.3 (統計) +/- 1.7 (系統) +/- 0.4 (ルミノシティ) nb であった。.
643. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a heavy Standard Model Higgs boson in the channel H->ZZ->llqq using the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2011.11.056, 707.0, 1.0, 27-45, 2012.01, 重い標準模型ヒッグスボソンで H->ZZ->llqq (l=e,mu) に崩壊するものの探索について発表する。探索は、CERN LHC のアトラス検出器で2011年に収集された積分ルミノシティ 1.04 fb-1 に相当する、重心系エネルギー 7 TeV での pp 衝突データを用いて行った。評価された背景事象を超える優位な超過は見られなかった。 生成断面積 (標準模型の期待する値に対して)の95% CL での上限は、200 - 600 GeV の質量範囲で導出した。排除する感度は現在ないが、最大感度の 360 GeV で、上限は 1.7 倍 (観測値)、2.7 倍 (予想値)、標準模型より大きかった。.
644. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the transverse momentum distribution of W bosons in pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.85.012005, 85.0, 1.0, 012005, 2012.01, 2010年の LHC での重心系エネルギー 7 TeV ランで、アトラス実験で得られた約 31 pb-1 の積分ルミノシティに相当する pp 衝突データを用い、W ボソンの横運動量分布の測定について記述する。W ボソンの電子崩壊とミューオン崩壊からの事象を両方用い、W の反跳によるカロリメータに残すエネルギーから、W 候補の横運動量を測定した。結果となる分布は、W ボソンの横運動量の関数として、正規化された微分断面積を得るように導出した。電子とミューオンのチャンネル、その組み合わせにおいて、300 GeV 以下の W ボソン横運動量に関する結果を得、摂動論的量子色力学といくつかのイベントジェネレータの予想と比較を行った。.
645. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the cross-section for b-jets produced in association with a Z boson at √s =7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2011.11.059, 706.0, 4-5, 295-313, 2012.01, 2010年にアトラス実験で収集した重心系エネルギー 7 TeV、 積分ルミノシティ約 36 pb-1 の pp 衝突データにおける、Z ボソンを伴う b ジェット生成の包含的断面積測定について発表する。高横運動量の電子またはミューオンに崩壊する Z ボソン、横運動量 25 GeV 以上でラピディティ 2.1 以下の変位崩壊点で同定された1つ以上の b ジェットを事象選別で要求した。背景過程を差し引き後、生成量を b ジェット候補の崩壊点質量分布から導出した。本断面積と包含的 Z ボソン 生成断面積の比 (Z ボソン事象あたりの平均 b ジェット数) も測定した。両結果は、主要項の次のオーダーでの摂動論的量子色力学の予想と良い一致を示した。.
646. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for New Phenomena in ttbar Events With Large Missing Transverse Momentum in Proton-Proton Collisions at √s = 7 TeV with the ATLAS Detector, Phys. Rev. Lett., 10.1103/PhysRevLett.108.041805, 108.0, 4.0, 041805, 2012.01, 2011年に収集した重心系エネルギー7TeV、積分ルミノシティ1.04fb-1の陽子陽子衝突データを用いて、トップクォーク対と大きな横運動量欠損を持つ事象の探索を行った。標準模型の予測からのずれは見られず、トップクォーク対と未知の中性粒子に崩壊する重い粒子に対する制限を付けた。.
647. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for supersymmetry in final states with jets, missing transverse momentum and one isolated lepton in √s = 7 TeV pp collisions using 1 fb-1 of ATLAS data, Phys. Rev. D, 10.1103/PhysRevD.85.012006, 85.0, 1.0, 012006, 2012.01, 2011年に収集した重心系エネルギー7TeV、積分ルミノシティ1.04fb-1の陽子陽子衝突データを用いて、大きな横運動量欠損、ジェット、および孤立したレプトンを持つ事象により、超対称性粒子の探索を行った。その結果、標準模型の予測を超える事象は観測されず、生成断面積に制限を付け、超重力モデルの元で超対称性パラメータに制限を付けた。.
648. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the ZZ production cross section and limits on anomalous neutral triple gauge couplings in proton-proton collisions at √s =7 TeV with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.108.041804, 108.0, 4.0, 041804, 2012.01, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ34pb-1の陽子陽子衝突データを用いて、b-ハドロンを含む2ジェット事象の生成断面積を測定した。その結果をNLO-QCDの予測と比較したところ、よく一致しているものの、大きな横運動量の領域ではうまく記述できていないことがわかった。.
649. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Kshort and Lambda production in pp interactions at √s = 0.9 and 7 TeV measured with the ATLAS detector at the LHC, Phys. Rev. D, 10.1103/PhysRevD.85.012001, 85.0, 1.0, 012001, 2012.01, 重心系エネルギー0.9TeVと7TeVの陽子陽子衝突におけるKshort中間子とΛ粒子の生成断面積を測定した。様々なモンテカルロシミュレーションの予測と比較したところ、Kshort中間子の分布は15%の精度で一致するものの、Λ粒子の横運動量分布を説明することが難しいことがわかった。.
650. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Kshort and Lambda production in pp interactions at √s = 0.9 and 7 TeV measured with the ATLAS detector at the LHC, Phys. Rev. D, 10.1103/PhysRevD.85.012001, 85, 1, 012001, 2012.01, 重心系エネルギー0.9TeVと7TeVの陽子陽子衝突におけるKshort中間子とΛ粒子の生成断面積を測定した。様々なモンテカルロシミュレーションの予測と比較したところ、Kshort中間子の分布は15%の精度で一致するものの、Λ粒子の横運動量分布を説明することが難しいことがわかった。.
651. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the ZZ production cross section and limits on anomalous neutral triple gauge couplings in proton-proton collisions at √s =7 TeV with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.108.041804, 108, 4, 041804, 2012.01, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ34pb-1の陽子陽子衝突データを用いて、b-ハドロンを含む2ジェット事象の生成断面積を測定した。その結果をNLO-QCDの予測と比較したところ、よく一致しているものの、大きな横運動量の領域ではうまく記述できていないことがわかった。.
652. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for supersymmetry in final states with jets, missing transverse momentum and one isolated lepton in √s = 7 TeV pp collisions using 1 fb-1 of ATLAS data, Phys. Rev. D, 10.1103/PhysRevD.85.012006, 85, 1, 012006, 2012.01, 2011年に収集した重心系エネルギー7TeV、積分ルミノシティ1.04fb-1の陽子陽子衝突データを用いて、大きな横運動量欠損、ジェット、および孤立したレプトンを持つ事象により、超対称性粒子の探索を行った。その結果、標準模型の予測を超える事象は観測されず、生成断面積に制限を付け、超重力モデルの元で超対称性パラメータに制限を付けた。.
653. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for New Phenomena in ttbar Events With Large Missing Transverse Momentum in Proton-Proton Collisions at √s = 7 TeV with the ATLAS Detector, Phys. Rev. Lett., 10.1103/PhysRevLett.108.041805, 108, 4, 041805, 2012.01, 2011年に収集した重心系エネルギー7TeV、積分ルミノシティ1.04fb-1の陽子陽子衝突データを用いて、トップクォーク対と大きな横運動量欠損を持つ事象の探索を行った。標準模型の予測からのずれは見られず、トップクォーク対と未知の中性粒子に崩壊する重い粒子に対する制限を付けた。.
654. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the inclusive isolated prompt photon cross-section in pp collisions at √s = 7 TeV using 35 pb-1 of ATLAS data, Phys. Lett. B, 10.1016/j.physletb.2011.11.010, 706.0, 2-3, 150-167, 2011.12, 重心系エネルギー 7 TeV での pp 衝突における、孤立したプロンプト光子の包含的生成に関する微分断面積の測定について発表する。測定は、擬ラピディティ 1.37 以下、1.52 - 2.37 の範囲で、横方向エネルギー 45 - 400 GeV の範囲で行った。結果は、LHC のアトラス検出器で収集された 35 pb-1 の積分ルミノシティに基づく。信号光子の生成量は、光子候補の周りの狭いコーン内のハドロンエネルギーの分布と光子選別に基づく、データを用いた手法により測定された。結果は、主要項の次の次数における摂動論的量子色力学の計算と比較され、断面積において 4 桁を超える範囲で良い一致を示した。.
655. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for dilepton resonances in pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.107.272002, 107.0, 27.0, 272002, 2011.12, 2個のレプトンに崩壊する、幅が狭く高い質量をもつ共鳴の探索について報告する。データは、LHC の重心系エネルギー 7 TeV での pp 衝突においてアトラス実験で収集され、ee (mumu) チャンネルで積分ルミノシティ 1.08 fb-1 (1.21 fb-1) に相当する。標準模型の予想を超える統計的に優位な超過は見られず、断面積と 2個のレプトンに崩壊する Z' 共鳴とランドール-サンドラム重力子の崩壊比との積に対して、共鳴の質量の関数として95% CL での上限を付けた。順次的標準模型 Z' ボソンについて 1.83 TeV の質量下限値を付けた。k/M_Pl=0.1 の結合を持つランドール-サンドラム重力子は、95% CL で 1.63 TeV 以下の質量が棄却された。.
656. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the Z to tau tau cross section with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.84.112006, 84.0, 11.0, 112006, 2011.12, LHC のアトラス実験で、ミューオン-ハドロン、電子-ハドロン、電子-ミューオン、ミューオン-ミューオンの、4つの異なる終状態を用い、タウ対に崩壊する Z ボソンの断面積を測定した。解析は、重心系エネルギー 7 TeV の陽子-陽子衝突で、積分ルミノシティ 36 pb-1 に相当するデータに基づく。高い検出器アクセプタンスの基準領域とフルの位相空間において、66 - 116 GeV の質量範囲で各終状態で断面積測定を行った。各断面積を組み合わせ、総 Z ボソン生成断面積と崩壊比の積は 0.97 +/- 0.07(統計) +/- 0.06(系統) +/- 0.03(ルミノシティ) と測定され、NNLO 計算と一致した。.
657. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a heavy neutral particle decaying into an electron and a muon using 1 fb-1 of ATLAS data, Eur. Phys. J. C, 10.1140/epjc/s10052-011-1809-9, 71.0, 12.0, 1809.0, 2011.12, 2011年に収集した重心系エネルギー7TeV、積分ルミノシティ1.07fb-1の陽子陽子衝突データを用いて、電子とミュー粒子の対に崩壊する重い中性粒子の探索を行った。その結果は標準模型の予測と矛盾せず、Rパリティを破るスカラータウ粒子とレポトンフレーバーを保存しないZ'粒子生成に制限を付けた。.
658. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at √s = 7 TeV with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-011-1846-4, 71.0, 12.0, 1846, 2011.12, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ34pb-1の陽子陽子衝突データを用いて、b-ハドロンを含む2ジェット事象の生成断面積を測定した。その結果をNLO-QCDの予測と比較したところ、よく一致しているものの、大きな横運動量の領域ではうまく記述できていないことがわかった。.
659. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for massive colored scalars in four-jet final states in √s =7 TeV proton-proton collisions with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-011-1828-6, 71.0, 12.0, 1828.0, 2011.12, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ34pb-1の陽子陽子衝突データを用いて、4ジェット終状態に崩壊する重い粒子の探索を行った。標準模型からのずれは観測されず、スカラーグルオンの質量に対して制限を加えた。.
660. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the Upsilon(1S) Production Cross-Section in pp Collisions at √s = 7 TeV in ATLAS, Phys. Lett. B, 10.1016/j.physletb.2011.09.092, 705.0, 1-2, 9-27, 2011.11, 重心系エネルギー 7 TeV での陽子-陽子衝突における Upsilon(1S) -> mu+mu- の生成断面積の測定を発表する。ラピディティ 1.2 以下、1.2 - 2.4 の 2 ビンにおける Upsilon(1S) の横運動量の関数として、断面積を測定した。測定では、よく理解されいない偏極度に依存するアクセプタンスにおける理論的不定性を押さえるために、両方のミューオンが横運動量 4 GeV 以上、擬ラピディティ 2.5 以下であることを要求した。結果は、LHC のアトラス検出器で収集された、積分ルミノシティ 1.13 pb-1 に基づく。断面積測定は理論予想と比較された:PYTHIA にあるカラー1重項とカラー8重項行列要素を含むNRQCD 模型の予想と因子2の範囲で一致したが、カラー1重項模型における主要項の次の次数での予想とは因子10までの範囲で一致しなかった。.
661. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena with the monojet and missing transverse momentum signature using the ATLAS detector in √s = 7 TeV proton-proton collisions, Phys. Lett. B, 10.1016/j.physletb.2011.10.006, 705.0, 4.0, 294-312, 2011.11, 重心系エネルギー 7 TeV での陽子-陽子衝突において、高いエネルギーのジェットと消失横運動量を持つ事象における新現象の探索について発表する。データは、LHC のアトラス検出器で収集され、積分ルミノシティ 33 pb-1 に相当する。観測された事象数は標準模型の予想と無矛盾であり、本結果は大きな余剰次元模型における制限という観点で解釈される。.
662. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of multi-jet cross-sections in proton-proton collisions at 7 TeV center-of-mass energy, Eur. Phys. J. C, 10.1140/epjc/s10052-011-1763-6, 71.0, 11.0, 1763.0, 2011.11, アトラス検出器を用い、重心系エネルギー 7 TeV での陽子-陽子衝突において、包含的な多重ジェット生成を研究した。データは積分ルミノシティ 2.4 pb-1 に相当する。多重ジェット断面積の結果を、主要項とパートンシャワーのモンテカルロ予想、ならびに、主要項の次の次数での QCD 計算と比較した。.
663. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the transverse momentum distribution of Z/gamma* bosons in proton-proton collisions at √s =7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2011.10.018, 705.0, 5.0, 415-434, 2011.11, 重心系 7 TeV の陽子-陽子衝突における Z/gamma* の横運動量分布の測定について発表する。データはアトラス検出器で収集され、電子対とミューオン対への崩壊チャンネルを用い、積分ルミノシティは 35 pb-1 (電子対)、40 pb-1 (ミューオン対)に相当する。規格化された微分断面積を、350 GeV までの横運動量でレプトン対不変質量 66 - 116 GeV の範囲で、電子とミューオンチャンネル別々に、またその組み合わせで測定した。測定を摂動論的 QCD と様々なイベントゲネレータの予想と比較した。固定次数摂動論的 QCD と組み合わせた再加重法 QCD の予想は、データと良い一致を示した。.
664. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for neutral MSSM Higgs bosons decaying to tau^+ tau^- pairs in proton-proton collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2011.10.001, 705.0, 3.0, 174-192, 2011.11, LHC のアトラス検出器を用いた、タウレプトン対に崩壊する中性ヒッグスボソンの探索について発表する。解析は、2010年に収集された重心系エネルギー 7 TeV の陽子-陽子衝突で、積分ルミノシティ 36 pb-1 のデータに基づく。信号選別の後、276 事象をデータサンプルで見つけた。その事象は、269 +/- 36 事象数の予想される背景事象と無矛盾であった。一般的なヒッグスボゾンついてはその質量の関数として、最小超対称性模型 (MSSM) における A/H/h 生成に関しては m_A と tan(beta) の関数として、生成断面積について95% CL での棄却制限を導出した。.
665. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a heavy gauge boson decaying to a charged lepton and a neutrino in 1 fb-1 of pp collisions at √s =7 TeV using the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2011.09.093, 705.0, 1-2, 28-46, 2011.11, LHC のアトラス検出器で、荷電レプトン (電子またはミューオン) とニュートリノに崩壊する重い荷電ゲージボソン (W') のような、高い質量を持つ状態の探索を行った。結果は、重心系エネルギー 7 TeV の pp 衝突で、積分ルミノシティ 1.04 fb-1 のデータの解析に基づく。標準模型の予想を超える超過は見られなかった。順次的標準模型の結合を持つ W' は、95% CL で 2.15 TeV の質量まで棄却された。.
666. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Higgs boson in the two photon decay channel with the ATLAS detector at the LHC, Phys. Lett. B, 10.1016/j.physletb.2011.10.051, 705.0, 5.0, 452-470, 2011.11, アトラス検出器で収集した重心系エネルギー 7 TeV、積分ルミノシティ 1.08 fb-1 の陽子-陽子衝突でデータを用い、 二つの光子に崩壊する標準模型ヒッグスボソンの探索について報告する。110 - 150 GeV の質量領域で優位な超過は見られなかった。この質量領域において、断面積と崩壊比の積に対する上限は、標準模型による予想の 2.5 - 5.8 倍であった。.
667. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a Standard Model Higgs boson in the H->ZZ->llnunu decay channel with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.107.221802, 107.0, 22.0, 221802, 2011.11, 2011年に収集した重心系エネルギー7TeV、積分ルミノシティ1.04fb-1の陽子陽子衝突データを用いて、ヒッグス粒子がH→ZZ→llnunuのに崩壊する事象の探索を行った。その結果が背景事象の予測と一致していることからヒッグス粒子の生成断面積に制限を付け、特に標準模型ヒッグス粒子について質量340GeVから450GeVの領域を棄却した。.
668. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Higgs boson in the H->WW->lvjj decay channel in pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Rev. Lett., 10.1103/PhysRevLett.107.231801, 107.0, 23.0, 231801, 2011.11, 2011年に収集した重心系エネルギー7TeV、積分ルミノシティ1.04fb-1の陽子陽子衝突データを用いて、ヒッグス粒子がH→WW→lnujjのように崩壊する事象の探索を行った。背景事象の予測を超える事象は観測されず、ヒッグス粒子の質量240GeVから600GeVの領域で生成断面積に上限をつけた。.
669. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the jet fragmentation function and transverse profile in proton-proton collisions at a center-of-mass energy of 7 TeV with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-011-1795-y, 71.0, 11.0, 1795.0, 2011.11.
670. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for the Standard Model Higgs boson in the decay channel H -> ZZ(*) -> 4l with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2011.10.034, 705.0, 5.0, 435-451, 2011.11, 2011年に収集した重心系エネルギー7TeV、積分ルミノシティ2.1fb-1の陽子陽子衝突データを用いて、ヒッグス粒子がH→ZZ(*)→4lのように崩壊する事象の探索を行った。ヒッグス粒子の質量110GeVから600GeVの領域で生成断面積に上限をつけ、191–197, 199–200 and 214–224 GeVの領域で標準模型ヒッグス粒子の存在を棄却した。.
671. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for new phenomena in final states with large jet multiplicities and missing transverse momentum using √s = 7 TeV pp collisions with the ATLAS detector, JHEP, 10.1007/JHEP11(2011)099, 2011.0, 11.0, 099, 2011.11, 2011年に収集した重心系エネルギー7TeV、積分ルミノシティ1.34fb-1の陽子陽子衝突データを用いて、6個以上のジェットと大きな横運動量欠損を持つ事象の探索を行った。標準模型からのずれは見られず、超対称性理論のモデルに制限を与えた。.
672. C. Adloff, K. Kawagoe et al. (The CALICE collaboration), Effects of high-energy particle showers on the embedded front-end electronics of an electromagnetic calorimeter for a future lepton collider, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 10.1016/j.nima.2011.06.056, 654, 1, 97-109, 2011.10.
673. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Diphoton Events with Large Missing Transverse Energy with 36 pb-1 of 7 TeV Proton-Proton Collision Data with the ATLAS Detector, Eur. Phys. J. C, 10.1140/epjc/s10052-011-1744-9, 71.0, 10.0, 1744.0, 2011.10, 重心系エネルギー 7 TeV で 36 pb-1 の陽子-陽子衝突データを用い、アトラス共同研究は大きな消失横方向エネルギーを持つ光子対の探索を行った。標準模型の予想を超える超過事象は見られず、新物理に関する断面積を 95% CL での上限を付けた。その上限は、bino のような最も軽いニュートラリーノを持つゲージ媒介による超対称性の破れ (GGM) の一般化されたモデルについては 0.38 - 0.65 pb、一つの統一余剰次元 (UED) を持つ特定の模型については 0.18 - 0.23 pb であった。50 GeV 以上の bino 質量に関して、560 GeV の 95% CL 下限値を GGM グルーイノ質量に付け、UED コンパクト化半径 R について、1/R > 961 GeV の下限値を付けた。これらの制限は、これらの模型に対して、今日までの最も厳しいテストを与える。.
674. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Inclusive search for same-sign dilepton signatures in pp collisions at √s = 7 TeV with the ATLAS detector, JHEP, 10.1007/JHEP10(2011)107, 2011.0, 10.0, 107.0, 2011.10, 同符号電荷を持つ2個の孤立レプトン (電子またはミューオン) を含む事象における、新物理に関する包含的探索について発表する。データは、アトラス検出器で収集された、重心系エネルギー 7 TeV での pp 衝突でアトラス検出器で収集され、積分ルミノシティ 34 pb-1 に相当する。2個のレプトンの不変質量、消失横運動量、ジェット多重度のスペクトルを標準模型と比較した。2個の電子、2個のミューオン、電子-ミューオンのチャンネルにおける、同符号の高い質量を持つレプトン対事象で、新しい起源の基準領域での断面積について制限を付けた。同符号のレプトン対信号を予想する4つ模型に制限を与えた:マヨナラニュートリノ、超対称性または統一余剰次元に類似したカスケードトポロジー、第4世代ダウン型クォーク。新物理のスケールを 1 TeV と仮定して、460 GeV 以下の実効作用素 V で生成されるマヨナラニュートリノは 95% CL で棄却された。第4世代ダウン型クォークについては、290 GeV の下限値を 95 % CL で付けた。.
675. G. Abbiendi, K. Kawagoe et al. (The OPAL Collaboration), Determination of alpha(S) using OPAL hadronic event shapes at root s=91-209 GeV and resummed NNLO calculations, PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 10.1140/epjc/s10052-011-1733-z, 71, 9, 2011.09.
676. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the Inelastic Proton-Proton Cross-Section at √s = 7 TeV with the ATLAS Detector, Nature Commun., 10.1038/ncomms1472, 2.0, 463.0, 2011.09, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ20μb-1の陽子陽子衝突データを用いて、陽子陽子非弾性衝突の断面積の測定を世界で初めて行った。事象は前方方向に設置したシンチレーション検出器にヒットがあるものを選び出した。測定値は60.3mbで、精度は3.5%であった。この測定値は現象論的予測と一致するものである。.
677. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the differential cross-sections of inclusive, prompt and non-prompt J/psi production in proton-proton collisions at √s = 7 TeV, Nucl. Phys. B, 10.1016/j.nuclphysb.2011.05.015, 850.0, 3.0, 387-444, 2011.09, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ2.3pb-1の陽子陽子衝突データを用いて、J/psi粒子の包括的生成断面積とBハドロンの崩壊により生成されたJ/psi粒子の割合を測定した。測定範囲は横運動量が1GeVから70GeV、ラピディティの絶対値が2.4未満で、今までで最も広範囲のものである。測定結果を量子色力学に基づくいくつかの理論計算と比較した。.
678. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of Wgamma and Zgamma production in proton-proton collisions at √s =7 TeV with the ATLAS Detector, JHEP, 10.1007/JHEP09(2011)072, 2011.0, 9.0, 72.0, 2011.09, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ35pb-1の陽子陽子衝突データを用いて、高エネルギーの光子を伴うW粒子とZ粒子の生成について研究した。得られた候補事象は、W粒子では約200事象、Z粒子では約50事象であった。生成断面積や運動学的分布は標準模型に基づく予測値と一致した。.
679. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Limits on the production of the Standard Model Higgs Boson in pp collisions at √s =7 TeV with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-011-1728-9, 71.0, 9.0, 1728.0, 2011.09, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ40pb-1の陽子陽子衝突データを用いて、標準模型ヒッグス粒子の探索を2個のゲージボソン(光子、Z粒子、W粒子)に崩壊するチャンネルで行なった。質量110-600GeVの範囲で生成断面積の信頼度95%の上限を付け、特に250GeV以上では今までで最も厳しい制限が得られた。.
680. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Heavy Long-Lived Charged Particles with the ATLAS detector in pp collisions at √s = 7 TeV, Phys. Lett. B, 10.1016/j.physletb.2011.08.042, 703.0, 4.0, 428-446, 2011.09, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ37pb-1の陽子陽子衝突データを用いて、衝突点から遠いミューオン検出器まで到達するほど長寿命な未知の荷電粒子の探索を行った。そのような粒子は標準模型を超える超対称性を持つ理論の一部で予言されるが、そのような信号は得られず、それらの理論に制限を付けた。.
681. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of dijet production with a veto on additional central jet activity in pp collisions at √s =7 TeV using the ATLAS detector, JHEP, 10.1007/JHEP09(2011)053, 2011.0, 9.0, 53.0, 2011.09, ジェット対の系で境界が決められたラピディティ領域における、ジェットの活性度の測定を発表する。事象は、20 GeV 以上の横運動量を持つジェットが2個の境界ジェットの間にある場合は、棄却する。その棄却法で生き残るジェット対事象の割合を、6単位ラピディティまで離れ、平均横運動量 50 - 500 GeV を持つ境界ジェットに関して示す。棄却スケール以上のジェットの平均多重度を、摂動論的 QCD 放出を定量化する別の方法として示す。データを、POWHEG-BOX (主要項の次の次数とパートンシャワーの組み合わせ) 、HEJ 計算を用いた全次数再加重法、PYTHIA, HERWIG++ そして ALPGEN イベントジェネレータからの予想と比較する。測定は、2010年にアトラス検出器により、重心系エネルギー 7 TeV での pp 衝突においてなされた。.
682. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Properties of jets measured from tracks in proton-proton collisions at center-of-mass energy √s = 7 TeV with the ATLAS detector, Phys. Rev. D, 10.1103/PhysRevD.84.054001, 84.0, 5.0, 054001, 2011.09, LHC での重心系エネルギー 7 TeV の陽子-陽子衝突において、アトラス内部検出器で測定した荷電粒子を用い、ジェットを同定してその性質を研究した。事象選別では最小バイアストリガーを用い、非常に低い横運動量を持つジェットを測定し、高運動量で十分摂動論的なジェットへ遷移する領域での特徴を研究した。ジェットは、反 kt アルゴリズムを荷電粒子に適用し、0.4 と 0.6 の二つの半径変数を選択して再構成した。包含的荷電ジェット横運動量断面積を 4- 100 GeV で測定し、ラピディティ 1.9 までの 4 つの領域で、荷電粒子レベルの真のジェットへ補正して示す。ジェット中の荷電粒子における横運動量と縦運動量の比を、ジェット軸からの半径距離の関数として、荷電粒子多重度と粒子密度とともに測定した。既存の調整されたモンテカルロイベントジェネレータに導入されている理論模型とデータを比較し、全体的に妥当な一致を示した。この比較は、モンテカルロのパートンシャワー、ハドロン化、ソフトな物理模型に感度がある。.
683. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in √s =7 TeV proton proton collisions, Phys. Lett. B, 10.1016/j.physletb.2011.05.061, 701.0, 2.0, 186-203, 2011.07, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ35pb-1の陽子陽子衝突データを用いて、終状態にジェットと消失横運動量を持ち、電子やミューオンを持たないようなスクォークとグルイーノの崩壊を探索した。標準模型を超える事象は観測されず、いくつかの超対称性理論に対して今まで最も厳しい制限を付けた。.
684. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for supersymmetry in pp collisions at √s = 7TeV in final states with missing transverse momentum and b-jets, Phys. Lett. B, 10.1016/j.physletb.2011.06.015, 701.0, 4.0, 398-416, 2011.07, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ35pb-1の陽子陽子衝突データを用いて、大きな消失運動量と少なくとも1つの重いクォークのジェットに崩壊する超対称性粒子の探索を行った。観測された事象は標準模型の予測する背景事象と無矛盾であり、Rパリティを保存する超対称性模型においてスボトム粒子とストップ粒子の質量が信頼度95%で、それぞれ590GeV以上、520GeV以上であるという制限を付けた。.
685. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for an excess of events with an identical flavour lepton pair and significant missing transverse momentum in √s = 7 TeV proton-proton collisions with the ATLAS detector, Eur. Phys. J. C, 10.1140/epjc/s10052-011-1647-9, 71.0, 7.0, 1647.0, 2011.07, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ35pb-1の陽子陽子衝突データを用いて、異符号で同じフレーバーの2個のレプトンと大きな消失横運動量の終状態に崩壊する超対称性粒子の生成を探索した。このフレーバーの相関を要求するモードは超対称性粒子の質量を測定する良いものであるが、標準模型の予測を超える事象は観測されなかったため、24個のパラメータを持つ超対称性標準模型のパラメータ空間に制限を付けた。.
686. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for supersymmetric particles in events with lepton pairs and large missing transverse momentum in √s = 7 TeV proton-proton collisions with the ATLAS experiment, Eur. Phys. J. C, 10.1140/epjc/s10052-011-1682-6, 71.0, 7.0, 1682.0, 2011.07, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ35pb-1の陽子陽子衝突データを用いて、異符号もしくは同符号の2個の孤立したレプトンと消失横運動量の終状態に崩壊する超対称性粒子の生成を探索した。標準模型の予測を超える事象は観測されなかったので、いくつかの超対称性を持つ理論モデルにおいて、スクォークの質量に制限を付けた。.
687. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Contact Interactions in Dimuon Events from pp Collisions at √s = 7 TeV with the ATLAS Detector, Phys. Rev. D, 10.1103/PhysRevD.84.011101, 84.0, 1.0, 011101(R), 2011.07, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ42pb-1の陽子陽子衝突データのミューオン対生成事象を用いて、標準模型を超える現象を記述し得る4フェルミオン接触相互作用の探索を行った。ミューオン対の質量分布は標準模型で予測されるものと一致し、接触相互作用のエネルギースケールの今までで最も厳しい下限値を得た。.
688. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the WW cross section in √s = 7 TeV pp collisions with ATLAS, Phys. Rev. Lett., 10.1103/PhysRevLett.107.041802, 107.0, 4.0, 041802, 2011.07, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ34pb-1の陽子陽子衝突データを用いて、W粒子対の生成断面積を孤立した2個のレプトンを要求することで測定した。候補が8事象見つかり、背景事象を考慮した生成断面積は標準模型に基づく予測値と一致した。.
689. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for high-mass states with one lepton plus missing transverse momentum in proton-proton collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2011.05.043, 701.0, 1.0, 50-69, 2011.06, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ36pb-1の陽子陽子衝突データを用いて、荷電レプトンとニュートリノに崩壊する質量の大きなゲージボソンの探索を行った。標準模型を超える事象は観測されず、そのような粒子を持つ理論模型に対して制限を付けた。.
690. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for stable hadronising squarks and gluinos with the ATLAS experiment at the LHC, Phys. Lett. B, 10.1016/j.physletb.2011.05.010, 701.0, 1.0, 1-19, 2011.06, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ34pb-1の陽子陽子衝突データを用いて、長寿命のスクォークとグルイーノの探索を行った。標準模型を超える事象は観測されなかったので、様々な超対称性模型に対して今まで最も厳しい制限を付けた。.
691. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the Muon Charge Asymmetry from W Bosons Produced in pp Collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2011.05.024, 701.0, 1.0, 31-49, 2011.06, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ31pb-1の陽子陽子衝突データを用いて、W粒子から崩壊してできるミューオンの電荷の非対称性をミューオンの擬ラピディティの関数として測定した。陽子中のアップクォークとダウンクォークの分布についての情報を得るため、測定結果を様々なパートン分布関数を用いた理論計算と比較した。.
692. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for a heavy particle decaying into an electron and a muon with the ATLAS detector in √s = 7 TeV pp collisions at the LHC, Phys. Rev. Lett., 10.1103/PhysRevLett.106.251801, 106.0, 25.0, 251801, 2011.06, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ35pb-1の陽子陽子衝突データを用いて、電荷の異なる電子とミューオンの対に崩壊する質量の大きな粒子の探索を行った。観測された事象は標準模型の予測する背景事象と無矛盾であり、Rパリティを破る超対称性模型やレプトンフレーバーを破る理論模型に対して、Tevatron加速器での実験よりも厳しい制限を付けた。.
693. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for high mass dilepton resonances in pp collisions at √s =7 TeV with the ATLAS experiment, Phys. Lett. B, 10.1016/j.physletb.2011.04.044, 700.0, 3-4, 163-180, 2011.06, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ40pb-1の陽子陽子衝突データを用いて、質量の大きな電子対もしくはミューオン対の共鳴状態を探索した。質量が110GeV以上の領域で標準模型の予測を超える事象は観測されなかった。いくつかの理論模型ではそのような共鳴状態を持つので、その質量に対して制限を付けた。.
694. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for pair production of first or second generation leptoquarks in proton-proton collisions at √s = 7 TeV using the ATLAS detector at the LHC, Phys. Rev. D, 10.1103/PhysRevD.83.112006, 83.0, 11.0, 112006, 2011.06, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ35pb-1の陽子陽子衝突データを用いて、第1世代もしくは第2世代のスカラーレプトクォークの対生成を探索した。候補事象数は標準模型で予測される背景事象数と一致するものであり、レプトクォークの質量の今までで最も厳しい下限値を得た。.
695. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of underlying event characteristics using charged particles in pp collisions at √s = 900 GeV and 7 TeV with the ATLAS Detector, Phys. Rev. D, 10.1103/PhysRevD.83.112001, 83.0, 11.0, 112001, 2011.05, 2009年と2010年に収集した重心系エネルギー900GeVと7TeVの陽子陽子衝突データを用いて、運動量移行の大きな事象に付随して起こる事象に対して感度のある荷電粒子の分布を測定した。測定された荷電粒子数はLHC加速器のデータが得られる前に調整されたモンテカルロ事象生成器が予測するよりも大きかった。.
696. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Charged particle multiplicities in pp interactions measured with the ATLAS detector at the LHC, New J. Phys., 10.1088/1367-2630/13/5/053033, 13.0, 053033, 2011.05, 重心系エネルギー0.9TeV、2.36TeV、7TeVでの陽子陽子衝突データを用いて、荷電粒子数、荷電粒子の横運動量分布と擬ラピディティ分布、平均横運動量の荷電粒子数依存性を測定した。どの運動学的領域においても、測定した荷電粒子数は比較に用いた全てのモンテカルロ事象生成器が予測するものより大きかった。.
697. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurements of underlying-event properties using neutral and charged particles in pp collisions at 900 GeV and 7 TeV with the ATLAS detector at the LHC, Eur. Phys. J. C, 10.1140/epjc/s10052-011-1636-z, 71.0, 5.0, 1636.0, 2011.05, 2009年と2010年に収集した重心系エネルギー900GeVと7TeVの陽子陽子衝突データを用いて、荷電と中性の粒子流の相関を測定した。運動量移行の大きな事象に付随して起こる事象に対してこの相関は感度がある。この解析に用いたモンテカルロ事象生成器は測定結果を再現できず、この測定結果はモンテカルロ事象生成器のパラメータに制限を付けることに使うことができる。.
698. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for New Physics in Dijet Mass and Angular Distributions in pp Collisions at √s = 7 TeV Measured with the ATLAS Detector, New J. Phys., 10.1088/1367-2630/13/5/053044, 13.0, 053044, 2011.05, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ36pb-1の陽子陽子衝突データのジェット対の質量と角度分布を用いて、未知の相互作用や共鳴状態を探索した。ジェット対の質量3.5TeV以下で測定した結果は標準模型の予測する背景事象と無矛盾であり、標準模型を超える物理事象を含む理論模型に対して制限を付けた。.
699. C. Adloff, K. Kawagoe et al. (The CALICE collaboration), Electromagnetic response of a highly granular hadronic calorimeter, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 10.1088/1748-0221/6/04/P04003, 6, 2011.04.
700. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Luminosity Determination in pp Collisions at √s = 7 TeV Using the ATLAS Detector at the LHC, Eur. Phys. J. C, 10.1140/epjc/s10052-011-1630-5, 71.0, 4.0, 1630.0, 2011.04.
701. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of the production cross section for W-bosons in association with jets in pp collisions at √s = 7 TeV with the ATLAS detector, Phys. Lett. B, 10.1016/j.physletb.2011.03.012, 698.0, 5.0, 325-345, 2011.04, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ1.3pb-1の陽子陽子衝突データを用いて、0個から4個のジェットを付随するW粒子の生成断面積とそのジェットの横運動量分布を測定した。摂動的量子色力学の計算はそれぞれのジェットの数での測定結果を良く再現した。.
702. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Search for Massive Long-lived Highly Ionising Particles with the ATLAS Detector at the LHC, Phys. Lett. B, 10.1016/j.physletb.2011.03.033, 698.0, 5.0, 353-370, 2011.04, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ3.1pb-1の陽子陽子衝突データを用いて、質量が大きく、イオン化を良く引き起こすような粒子の探索を内部飛跡検出器と電磁カロリメータでのエネルギー損失を調べることで行なった。そのような粒子は発見されなかったので、その質量と電荷に対して制限を付けた。.
703. Georges Aad, Kiyotomo Kawagoe et al. (The ATLAS Collaboration), Measurement of Dijet Azimuthal Decorrelations in pp Collisions at √s =7 TeV, Phys. Rev. Lett., 10.1103/PhysRevLett.106.172002, 106.0, 17.0, 172002, 2011.04, 2010年に収集した重心系エネルギー7TeV、積分ルミノシティ36pb-1の陽子陽子衝突データを用いて、中心部の2つの横運動量の大きいジェットの角度分布を測定した。量子色力学はジェットの数が増えるにつれ、この角度分布が反対方向から等方的になることを予測する。測定結果と結合定数が4次の項まで含む量子色力学の理論計算の結果は良く一致した。.

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