包含相变的中子星自洽物态方程及其对重离子碰撞可观测量的影响
Neutron Stars consistent Equations of State with Phase Transitions and their Impact in Heavy Ion Collision Observables
AI总结：
该研究利用手征平均场框架构建含相变的中子星物态方程，将其植入UrQMD模型，发现重离子碰撞可观测量对该物态方程敏感，为探测相变提供潜在实验信号。
AI中文摘要：
我们采用手征平均场（Chiral Mean Field, CMF）框架，结合天体物理及格点量子色动力学（lattice QCD）的输入，探究不同物态方程（Equations of State, EoS）对重离子碰撞可观测量的影响。所研究的EoS家族可同时再现质量大于2倍太阳质量的中子星，且在约2倍核饱和密度处表现出一阶相变；这一结果是通过调整Δ共振与标量σ场、矢量ω场相较于核子的矢量与标量耦合相对比值实现的。我们将这些EoS与有限温度下的QCD迹异常进行对比，并将默认CMF EoS及带相变的修正EoS均植入UrQMD输运模型，从定性与定量层面研究相变的效应。具体而言，对束流能量0.5-3 GeV（即GSI/FAIR能区，对应HADES与CBM实验）的金-金（Au+Au）碰撞，观测到其对EoS存在明显敏感性；我们分析了质子的横动量分布、π⁺在快度中心区附近的定向流（direct flow, v₁）及其斜率，以及K⁺/π⁺比值。默认CMF EoS、修正EoS与级联模式所得结果间存在显著差异，尤其在π介子的v₁斜率及奇异粒子产生方面。这些发现表明重离子可观测量对核EoS具有敏感性，并凸显了相变的潜在实验信号。
英文摘要：
We explore the impact of different equations of state (EoS) on heavy ion collision observables using a Chiral Mean Field (CMF) framework constrained by astrophysical and lattice QCD inputs. The investigated family of EoS simultaneously reproduce neutron stars with masses above two solar masses and exhibit a first order phase transition around two times the nuclear saturation density. This is achieved by varying the relative vector and scalar couplings of $Δ$ resonances with the scalar $σ$ and vector $ω$ fields with respect to nucleons. These EoS are compared to the QCD trace anomaly at finite temperature. We implement both, the default CMF EoS and the modified EoS featuring a phase transition into the UrQMD transport model to study the effects of the phase transition on a qualitative and quantitative level. In particular Au+Au collisions at beam energies of 0.5-3 GeV, the GSI/FAIR energy range of the HADES and CBM experiments, shows visible sensitivity on the EoS. Transverse momentum distributions for protons, the directed flow ($v_1$) and its slope near mid-rapidity for $π^+$ as well as the $K^+/π^+$ ratio is analyzed. Clear differences emerge between the results obtained with the default CMF EoS, the modified EoS, and the cascade mode, particularly the slope of $v_1$ of the pions and in strangeness production. These findings demonstrate the sensitivity of heavy ion observables to the nuclear EoS and highlight potential experimental signatures of a phase transition.
