Emiko Hiyama | Last modified date：2020.03.05 |

Professor /
Department of Physics /
Faculty of Sciences

**Papers**

1. | E. Hiyama, K. Sasaki, T. Miyamoto, T. Doi, T. Hatsuda, Y. Yamamoto, and Th. A. Rijken, Possible Lightest Ξ Hypernucleus with Modern ΞN Interactions, Phys. Rev. Lett. 124, 092501 – Published 4 March 2020, https://doi.org/10.1103/PhysRevLett.124.092501, 092501-1-092501-5, Phys. Rev. Lett. 124, 092501 , 2020.03, [URL], Experimental evidence exists that the Ξ-nucleus interaction is attractive. We search for NNΞ and NNNΞ bound systems on the basis of the AV8 NN potential combined with either a phenomenological Nijmegen ΞN potential or a first principles HAL QCD ΞN potential. The binding energies of the three-body and four-body systems (below the d+Ξ and 3H/3He+Ξ thresholds, respectively) are calculated by a high precision variational approach, the Gaussian expansion method. Although the two ΞN potentials have significantly different isospin (T) and spin (S) dependence, the NNNΞ system with quantum numbers (T=0, Jπ=1+) appears to be bound (one deep for Nijmegen and one shallow for HAL QCD) below the 3H/3He+Ξ threshold. Experimental implications for such a state are discussed.. |

2. | Ulugbek Yakhshiev, Hyun Chul Kim, Emiko Hiyama, Instanton effects on charmonium states, Physical Review D, https://doi.org/10.1103/PhysRevD.98.114036, 98, 2018.12, [URL], The instanton effects on the charmonium spectrum are discussed in the framework of the nonrelativistic potential model. The results from the constituent quark model without inclusion of instanton effects are compared with the results for the potential from the constituent quark model plus the contribution from the instanton liquid model. We consider two models with the corresponding instanton potentials and discuss their relevance to explanations of the origin of phenomenological parameters used in the nonrelativistic potential models. We also present the universal instanton potential in a parametrized form, which can be useful in practical calculations.. |

3. | Emiko Hiyama, Masayasu Kamimura, Study of various few-body systems using Gaussian expansion method (GEM), Frontiers of Physics, 13, 2018.07, [URL], We review our calculation method, Gaussian expansion method (GEM), to solve accurately the Schrödinger equations for bound, resonant and scattering states of few-body systems. Use is made of the Rayleigh-Ritz variational method for bound states, the complex-scaling method for resonant states and the Kohn-type variational principle to S-matrix for scattering states. GEM was proposed 30 years ago and has been applied to a variety of subjects in few-body (3- to 5-body) systems, such as 1) few-nucleon systems, 2) few-body structure of hypernuclei, 3) clustering structure of light nuclei and unstable nuclei, 4) exotic atoms/molecules, 5) cold atoms, 6) nuclear astrophysics and 7) structure of exotic hadrons. Showing examples in our published papers, we explain i) high accuracy of GEM calculations and its reason, ii) wide applicability of GEM to various few-body systems, iii) successful predictions by GEM calculations before measurements. The total bound-state wave function is expanded in terms of few-body Gaussian basis functions spanned over all the sets of rearrangement Jacobi coordinates. Gaussians with ranges in geometric progression work very well both for shortrange and long-range behavior of the few-body wave functions. Use of Gaussians with complex ranges gives much more accurate solution than in the case of real-range Gaussians, especially, when the wave function has many nodes (oscillations). These basis functions can well be applied to calculations using the complex-scaling method for resonances. For the few-body scattering states, the amplitude of the interaction region is expanded in terms of those few-body Gaussian basis functions.. |

4. | Emiko Hiyama, Atsushi Hosaka, Makoto Oka, Jean Marc Richard, Quark model estimate of hidden-charm pentaquark resonances, Physical Review C, 10.1103/PhysRevC.98.045208, 98, 2018.10, [URL], A quark model, which reproduces the ground-state mesons and baryons, i.e., the threshold energies, is applied to the qqqcc configurations, where q is a light quark and c the charmed quark. In the calculation, several open channels are explicitly included such as J/ψ+N, ηc+N, Λc+D, etc. To distinguish genuine resonances and estimate their width, we employ the Gaussian expansion method supplemented by the real scaling method (stabilization). No resonance is found at the energies of the Pc(4380) and Pc(4450) pentaquarks. On the other hand, there is a sharp resonant state at 4690 MeV with a J=1/2- state and another one at 4920 MeV with a J=3/2- state which have a compact structure.. |

5. | R. Lazauskas, E. Hiyama, J. Carbonell, Ab ignition calculation of 5H resonant states, Physics Letters, 791, 335-341, 2019.04, [URL]. |

6. | Jehee Lee, Qian Wu, Yasuro Funaki, Hongshi Zong ad Emiko Hiyama, Three-body structure of 9ΛBe with αα cluster model, Few-body systems, https://doi.org/10.1007/s00601-019-1502-3, 2019.06, [URL], In the framework of \(\alpha +\alpha +\varLambda \) three-body cluster model, we calculate energy spectra from bound energy region to resonant energy region up to around 20 MeV with respect to \(\alpha \alpha \varLambda \) threshold. To calculate resonant states, we employ Complex Scaling method which is one of the powerful method. We obtain the states of \(^8\)Be analogue and genuine hypernuclear analogue, which are consistent with those by Yamada et al. (Prog Theor Phys Suppl 81:104, 1985). However, the calculated ordering of \(^9\)Be analogue states is quite different with their calculation. We also obtain \(2^+\) and \(4^+\) resonant states of which have been never pointed out.. |

7. | Emiko Hiyama and Kazuma Nakazawa, Structre of S=-2 hypernuclei and Hyperon-Hyperon Interaction, Annual Review of Nuclear and Particle Science, https://doi.org/10.1146/annurev-nucl-101917-021108, 68, 131-190, 2018.06, We review recent progress in $S=-2$ hypernuclei such as double $\Lambda$hypernuclei and $\Xi$ hypernucei, which are composed of a nucleus and one or two hyperons such as a $\Lambda$ or a $\Xi$ particle. By observation of $^6_{\Lambda \Lambda}$He, as the NAGARA event, we obtain important information on the $\Lambda \Lambda$ interaction. Using this information, we perform a four-body calculation of $\alpha \alpha \Lambda \Lambda$ for $^{10}_{\Lambda \Lambda}$Be which was observed at the KEK experiment as the DEMACHI-YANAGI event. We interpret this event to be the $2^+$ excited state. Energy levels of $^{11}_{\Lambda \Lambda}$Be are calculated within the framework of an $\alpha \alpha n \Lambda \Lambda$ five- body cluster model. Then, we interpret the HIDA event which was observed in the KEK experiment to be an observation of the ground state of $^{11}_{\Lambda \Lambda}$Be. Motivated by observation of the KISO event of $^{15}_{\Xi^-}$C, with use of SHF and RMF, we calculate the energy spectra of this hypernucleus. We interpret this event as the $^{14}{\rm N(g.s.)}+\Xi^-(0p)$ state. Finally We propose to perform an experiment of $^7{\rm Li}(K^-,K^+)^7_{\Xi^-}$H and $^{10}{\rm B}(K^-,K^+)^{10}_{\Xi^-}$Li in order to extract information about the spin- and isospin-averaged part of $\Xi N$ interaction.. |

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