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arXiv 2209.01413nucl-th
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在$\sqrt{s_\mathrm{NN}}=2.4-7.7$ GeV重离子碰撞中相变对2 π干涉的影响

Effects of a phase transition on two-pion interferometry in heavy-ion collisions at $\sqrt{s_\mathrm{NN}}=2.4-7.7$ GeV

Pengcheng Li, Jan Steinheimer, Tom Reichert, Apiwit Kittiratpattana, Marcus Bleicher, Qingfeng Li

摘要:

利用UrQMD模型,采用不同的状态方程,计算了在$\sqrt{s_\mathrm{NN}}=2.4 - 7.7~\text{GeV}$(对应于$E_{\rm{lab}}=1.23~\text{to}~30~\text{GeV/nucleon}$的固定靶坐标系中的束流动能)上Au+Au中心碰撞中带电π介子的Hanbury-Brown-Twiss(HBT)关联.在高重子密度的相变的影响,清楚地观察到在HBT的参数进行了探讨。结果表明,在所研究的能量范围内,关于HBT半径$R_{O}/R_{S}$和$R^{2}_{O}-R^{2}_{S}$的现有数据有利于在低束能量下形成一个相对刚性的状态方程,而在高碰撞能量下则转变为一个与QCD高密度状态方程的天体物理约束相一致的软状态方程.研究了两种不同的相变情形对$R_{O}/R_{S}$和$R^{2}_{O}-R^{2}_{S}$的影响。发现使用HBT数据可以排除状态方程在4倍核饱和密度以下显着软化的相变。我们的结果表明,π介子的$R_{O}/R_{S}$和$R^{2}_{O}-R^{2}_{S}$对状态方程的刚度是敏感的,可以用来约束和理解重子密度较高区域的QCD状态方程。

英文摘要:

Hanbury-Brown-Twiss (HBT) correlations for charged pions in central Au+Au collisions at $\sqrt{s_\mathrm{NN}}=2.4 - 7.7~\text{GeV}$ (corresponding to beam kinetic energies in the fixed target frame from $E_{\rm{lab}}=1.23~\text{to}~30~\text{GeV/nucleon}$) are calculated using the UrQMD model with different equations of state. The effects of a phase transition at high baryon densities are clearly observed in the HBT parameters that are explored. It is found that the available data on the HBT radii, $R_{O}/R_{S}$ and $R^{2}_{O}-R^{2}_{S}$, in the investigated energy region favors a relatively stiff equation of state at low beam energies which then turns into a soft equation of state at high collision energies consistent with astrophysical constraints on the high density equation of state of QCD. The specific effects of two different phase transition scenarios on the $R_{O}/R_{S}$ and $R^{2}_{O}-R^{2}_{S}$ are investigated. It is found that a phase transition with a significant softening of the equation of state below 4 times nuclear saturation density can be excluded using HBT data. Our results highlight that the pion's $R_{O}/R_{S}$ and $R^{2}_{O}-R^{2}_{S}$ are sensitive to the stiffness of the equation of state, and can be used to constrain and understand the QCD equation of state in the high baryon density region.

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