【直播】【复旦核物理前沿开放讲坛】Akira Ohnishi (大西 明) 教授 学术报告

报告题目：

Challenge to the hyperon puzzle – Density dependence of Λ potential in nuclear matter from heavy-ion collisions and hypernuclear spectroscopy

报告时间：

2023年1月4日（周三）14:00

报告嘉宾：

Akira Ohnishi (大西明) 教授 | 日本Kyoto University（京都大学）

主办单位：

复旦大学核科学与技术系/现代物理研究所

核物理与离子束应用教育部重点实验室

国家自然科学基金委-理论物理专款

上海核物理理论研究中心

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报告人介绍

Akira Ohnishi (大西 明) 教授

日本Kyoto University（京都大学）

Akira Ohnishi is a Professor at Yukawa Institute for Theoretical Physics, Kyoto University. He got the PhD at Kyoto University in 1992. After working at Osaka University and Hokkaido University, he took the current professorship since 2008. His primary research interests include lattice QCD, equation of state and phase diagram of quark-nuclear matter, strangeness, 2 and 3-body interaction, etc. He has published more than 230 articles and currently is the editor of Progress of Theoretical and Experimental Physics. He has also been serving in Physical Society of Japan, Nuclear Theory Group Committee and APCTP Japanese Committee.

报告简介

The hyperon puzzle is one of the primary problems in neutron star physics. Λ baryons are expected to appear in neutron star matter at (2-4)ρ0 when two-body interactions based on hypernuclear data are used, but hyperons soften the equation of state (EOS) and make it difficult to explain the existence of 2M⊙ neutron stars. Thus Λ should feel a strong repulsive potential in dense nuclear matter. Phenomenologically, it is possible to introduce repulsion at high density by introducing, for example, ΛΝΝ 3-body repulsion. It is also known that repulsion appears at high densities in model calculations based on the chiral effective field theory (chiral EFT) , but there is no experimental support for this repulsion.

We examine the density dependence of Λ potential (UΛ) in nuclear matter proposed by the chiral EFT via the heavy-ion collision data and hypernuclear spectroscopy. In Ref., we found that UΛ from chiral EFT successfully explains the directed flow of Λ provided that the momentum dependence is not strong. The momentum dependence of UΛ is closely related to the effective mass of Λ in hypernuclei, so we next examine UΛ from chiral EFT in hypernuclei. While the density dependence of UΛ from chiral EFT is significantly different from that in empirical ones, one can explain the Λ separation energy data equally well.

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