RHIC和SPS上夸克组合强子化机制的唯象学研究

Hadronization is one of open questions in quantum chromodynamics (QCD) in the non-perturbative regime. In relativistic heavy ion collisions, it is a key bridge between final-state observables and the quark gluon plasma (QGP) produced in early stage of collisions. RHIC physics show that the quark combination mechanism plays an important role in the hadronization of QGP. Recently, the Beam Energy Scan program of STAR Collaboration and SPS experiments at CERN found new features of hadron production in heavy ion collisions in the 5-20 GeV regions. For example, the quark number scaling for hadronic elliptic flow v2 is broken partially as the collision energy decreases to 11.5 GeV. Is the quark combination mechanism applicable in this energy region? Is QGP created? In this project, we will apply a quark combination model developed by Shandong Group to systematically study the production of thermal hadrons in a broad collisional energy region 5-200 GeV (from SPSto RHIC). We shall investigate yields and momentum distributions of various thermal hadrons, collective flows, baryon-antibaryon correlation and fluctuation to test the universality of quark combination mechanism and explore the threshold of QGP creation and the phase transition at lower SPS energies.

强子化是强相互作用理论的基本问题，也是相对论重离子碰撞中夸克胶子等离子体（QGP）与末态可观测量联系的关键。RHIC 物理研究表明：夸克组合是QGP 强子化的必要机制。最近STAR 的 Beam Energy Scan 实验和CERN 的SPS 实验在5-20GeV 能区发现了强子产生的新特征，如强子椭圆流的组分夸克数目标度性在11.5GeV被破坏。此能区夸克组合机制是否仍然适用? QGP新物质态是否产生？本项目将利用山东夸克组合模型对RHIC和SPS能区重离子碰撞中热强子的产生规律进行系统研究。通过对强子产额、动量谱、集体流、重子-反重子关联和涨落等性质的研究，检验夸克组合机制的普适性，深入理解强子化规律，探索较低SPS能区QGP的产生阈以及相变特征。

强子化是强相互作用理论的基本问题，也是相对论重离子碰撞中夸克胶子等离子体（QGP）与末态可观测量联系的关键。RHIC 物理研究表明：夸克组合是QGP 强子化的必要机制。最近STAR 的 Beam Energy Scan 实验在5-20GeV 碰撞能区发现了强子产生的新特征。本项目在之前的工作基础上开展了以下工作：（1）实验上观测到该能区的 $K^{-}/K^{+}$ 和 $\bar{p}/p$ 间的产额关联与RHIC高能区的实验结果是一致的，呈现出一种普适性。我们用夸克组合机制成功解释了该现象，表明组合机制能够应用到RHIC低能区。（2）详细研究了组合机制中各种强子产额的性质，较好解释了该能区各种轻强子产额的实验数据，并给出检验该能区组合机制适用性和QGP产生的特色预言。以上重要结果总结在1篇高质量的论文中并发表在Physical Review C。