QGP物质及其强子化动力学研究

Hadronization, the process of formation of hadrons out of final-state quarks and/or gluons in high energy reactions, is an important subject of quantum chromodynamics in non-perturbative regime. In relativistic heavy ion collisions, it serves as the key bridge between final-state observables and the quark gluon plasma (QGP) produced in early stage of collisions. The study of the hadronization is mainly carried out, at present, through the interactions between experimental data in high energy reactions and various phenomenological models. The quark combination model is an indispensable phenomenological mechanism of describing the hadronization of QGP, and has successfully explained lots of experimental data of hadron production (in different aspects) in AA collisions at RHIC energies. In the finishing project, we have applied the model to LHC energies and have obtained the positive results. Because of the non-perturbative difficulty of QCD, there still have many unsolved questions in quark combination dynamics, i.e., space-time evolution details of QGP hadronization via quark combination, the role of gluon at hadronization and the global thermodynamic characteristic of the system in combination process, etc. In this project, taking advantage of RHIC and LHC experiments of heavy ion collisions in broad energy range which produce the QGP with variant volume, energy density and baryon number density and have accumulated extremely rich experimental data, we will study the dynamic correlations and fluctuations of hadron production, charm hadron production, properties of resonance and exotic multi-quark state production in heavy ion collisions, and in these studies we will complete the dynamics of quark combination model by focusing on the solution of several key dynamic issues in combination process mentioned above, and meanwhile playing the bridge role of hadronization model, we will obtain/extract more information of QGP system produced in relativistic heavy ion collisions.

强子化（高能反应中末态夸克、胶子转化为强子的过程）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)与末态观测量联系的关键。其机制至今只能以唯象模型与实验的互动研究进行探索。夸克组合模型是描写QGP强子化的必要机制，已成功解释RHIC实验强子产生的一系列性质。在即将完成的课题中，我们将之应用到LHC能区，也取得较好结果。由于非微扰困难，夸克组合的动力学还有许多不清楚的地方，如QGP组合强子化的时空演化、胶子自由度的处理、组合过程的热力学特征等。本项目结合RHIC至LHC广阔能区的重离子碰撞实验，利用其能产生不同体积、不同能量密度和重子数密度的QGP系统和海量的实验数据，通过研究强子产生的动力学关联、涨落，粲强子、共振态和多夸克产生等，发展夸克组合模型，重点解决夸克组合过程中的上述关键动力学问题；以强子化为纽带，从末态实验数据中获取QGP物质的更多信息。

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)与末态观测量联系的关键。夸克组合是描写QGP强子化的有效机制，已成功解释了RHIC和LHC重离子碰撞中强子产生的一系列性质。由于非微扰困难，夸克组合的动力学尚有不清楚之处。本项目从以下四个方面研究了QGP强子化，取得了许多重要进展。（1）夸克组合动力学。发现了LHC能量pp和p+Pb碰撞高多重数事例中强子横动量谱的组份夸克数目标度性，这正是强子化时组份夸克等速度组合的直接结果。质心系能量√(s_NN )=11.5-2760GeV重离子碰撞中Ω和ϕ的横动量谱实验数据进一步验证了该标度性。这表明，组份夸克有效自由度在QGP强子化时起着重要作用。（2）粲夸克强子化。研究了粲夸克与轻味夸克的等速度组合强子化，成功解释了LHC能量pp、p+Pb以及重离子碰撞中D介子和Λ_c^+重子的中等横动量区实验数据。理论预言的Λ_c^+/D^0随横动量的非单调依赖性被ALICE最新实验数据证实。（3）多夸克态和共振态的产生。应用夸克组合模型研究了含粲偶素五夸克态的产生，预言了LHC能量重离子碰撞中Pc^+(4380)和Pc^+(4450)的产额和横动量谱。研究了重离子碰撞中K^(*0)(892)和ϕ(1020)等共振态的产生，应用夸克组合模型和UrQMD模型计算了强子化和强子重散射对共振态产生的贡献比例。（4）强子关联和涨落。基于夸克自由组合的统计方法，研究了强子多重数的关联和涨落，分析了强子化前夸克的关联涨落、夸克组合过程以及共振态衰变的影响，成功解释了STAR和ALICE实验的净质子数的累积矩比值以及K/π、p/π和K/p对涨落的实验数据。在这些研究中也反向获得了QGP的集体流、奇异性等性质。与此同时，对山东夸克组合模型从理论及技术上作了进一步完善和发展。以上重要结果总结为14篇高质量论文，得到了国内外同行的认可，发表在 Phys. Rev. C/D, Phys.Lett.B, Eur.Phys.J.C, Chin.Phys.C等学术期刊。