Hadronic Transport in J-PARC Energy Heavy-Ion Collisions Revisited

2017 Fiscal Year Final Research Report

• Project/Area Number: 15K05079
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: Kyoto University
• Principal Investigator: Ohnishi Akira 京都大学, 基礎物理学研究所, 教授 (70250412)
• Co-Investigator(Kenkyū-buntansha): 奈良 寧 国際教養大学, 国際教養学部, 教授 (70453008)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: 重イオン衝突 / 輸送方程式 / 衝突項 / 平均場 / QCD相転移 / J-PARC / 集団フロー / ビリアル定理

Outline of Final Research Achievements

We have demonstrated that the negative slope of the directed flow (negative flow) observed in heavy-ion collisions at the colliding energies around 10 GeV can be explained by introducing strong softening of the equation of state. At RHIC, the proton directed flow slope is found to become negative at colliding energies around 10 GeV per nucleon pair, while it increases again at higher energies. We cannot explain the negative flow at around 10 GeV in hadronic transport models even with potential effects, but we can explain it with strong softening of the equation of state implemented in the collision term based on the virial theorem. This strong softening is consistent with the existence of the QCD phase transition at baryon densities of (5-10) times of normal nuclear matter. Combined with other collective flows such as radial and elliptic flows, it is also possible to distinguish the softening from the first order transition, the crossover, and the hadronic potential effects.

Free Research Field

原子核物理学（理論）