QCD相结构与强相互作用物质性质的泛函重整化群研究

It is proposed in this project that, by employing the functional renormalization group (FRG) approach, we would like to investigate the two-flavor rebosonized QCD and the 2+1 flavor low energy effective models at finite temperature and nonvanishing densities. Then, based on these researches, we will construct the 2+1 flavor rebosonized QCD at finite temperature and densities, with the aid of the dynamical hadronization. Within the framework of the FRG rebosonized QCD and the low energy effective models, we will study the physical mechanisms for the chiral and deconfinement phase transitions at finite temperature and densities, QCD phase structure and phase diagram, QCD thermodynamics and the equation of state, and calculate the kurtosis and skewness of the baryon number distributions, fluctuations for the electric charge, correlations among conserved charges (the baryon number, electric charge and the strangeness) and so on. Furthermore, calculated physical observables, such as the higher moments of the baryon number and the electric charge distributions, correlations among conserved charges and so on, will be compared with the measurements in the beam energy scan experiments at RHIC. Emphases will be paid on the dependence of the observables on the collision energy, centrality, and the transverse momentum pT, which is aimed to provide theoretical explanations and predictions for the search of the QCD critical ending point.

本项目拟以泛函重整化群为理论方法，研究有限温度有限密度情况下，具有强子自由度的两味重玻色化（rebosonized）QCD，以及2+1味的低能有效模型。并且在此基础上利用动力学强子化构建2+1味的重玻色化QCD。在泛函重整化群重玻色化QCD以及低能有效模型的框架下，系统地研究有限温有限密手征相变和退禁闭相变的物理机制、QCD的相结构和相图、QCD热力学以及状态方程，计算重子数分布的峰度和偏斜度、电荷的涨落、守恒荷（重子数、电荷以及奇异数）之间的各阶关联等等。此外，将计算得到的重子数和电荷分布的高阶矩、守恒荷的关联等物理量与RHIC束流能量扫描实验的结果进行比较，考察观测量随对撞能量、中心度、横动量pT的依赖关系，为实验寻找QCD临界终点提供理论解释和预言。

近年来，量子色动力学（QCD）在极端环境下的性质，比如高温、高密、强磁场等等，以及相对论重离子碰撞物理的相关研究取得了很多重要的进展。其中，QCD相结构的研究是一个很重要的前沿热点，实验物理学家试图通过相对论重离子碰撞实验寻找QCD相图上的临界终点（CEP）。特别是，最近STAR合作组发现实验测量得到的净质子数峰度随束流能量变化具有非单调的依赖性。在该项目的资助下，项目课题组搭建了第一性原理泛函重整化群（FRG）有限温有限密量子色动力学的理论框架，并且将该理论框架应用于QCD相结构的研究，预言了QCD临界终点在相图上的位置，为RHIC束流能量扫描实验寻找QCD临界终点提供理论支持。此外，我们发现实验测量得到的质子数峰度的非单调性可能来源于低能碰撞区不断增强的连续过渡。相关的系列成果共发表了21篇论文（SCI论文20篇），其中 SciPost Physics 1篇，Physcial Review D 16篇（包括1篇ESI高被引和1篇编辑推荐论文），Astrophys. J. 1篇，Chinese Physics C 2篇，SciPost Physics Core 1篇（新期刊，尚未被SCI收录）。