Probing quark gluon plasma by heavy quarks in heavy-ion collisions

Theoretical calculations predict that hadronic matter at high temperatures and densities dissolves into a deconfined state of quarks and gluons - called Quark Gluon Plasma (QGP). In this state the hadrons, like protons and neutrons, which form the matter around us, have lost their identity and their constituents, quarks and gluons, can move freely in this plasma. This new state of matter existed at the beginning of the expansion of the Early Universe. Therefore, the study of QGP assumes special importance in understanding the evolution of the Early Universe. The issue is very crucial for astrophysics too, because the core of the compact astrophysical objects like neutron star may contain deconfined quark matter at high baryon density and low temperature. There is strong evidence that the QGP can be produced by colliding nuclei at Large Hadron Collider (LHC) and at Relativistic Heavy Ion Collider (RHIC) energies. The study of the properties of QGP is a field of high contemporary interest and the heavy hadrons (hadrons which contain at least one heavy quark) constitute a unique probe of the QGP properties, because they are produced in the early stage of the collisions and they are the witness to the entire space-time evolution of the system. In the frame of this proposal we will investigate how heavy hadrons can elucidate the properties of the QGP. For this we have first to study theoretically the interaction of these heavy hadrons with QGP. In a second step we can incorporate these theoretical results in a transport approach which simulates the whole heavy ion interaction on a computer. The comparison of the theoretical results with experiments will then allow for drawing conclusions on the QGP properties.

理论计算预言强子物质在高温高密度时将会演化成一种由夸克和胶子组成的退禁闭的态，也就是夸克胶子等离子体。夸克胶子等离子体存在于早期宇宙，所以对夸克胶子等离子体的研究对了解早期宇宙非常重要。有力的证据证明夸克胶子等离子体可以在LHC和RHIC的原子核碰撞实验中产生。其中重强子（至少包括一个重夸克）对研究夸克胶子等离子体的性质有着重要的意义。因为它在碰撞早期产生，并且参与了体系演化的全过程。在本项目中，我将着重研究重强子和夸克胶子等离子体性质的关系。首先我将研究这些强子和夸克胶子等离子体的相互作用，然后我们会将我们的研究结果和输运理论相结合，这样就使我们可以计算出实验可观测量的预言值。通过对比理论计算的值和实验观测数据，我们就可以对夸克胶子等离子体的性质有更清楚的认识。

根据广义相对论及宇宙学标准模型预言，在大爆炸发生几个微秒时，将形成夸克胶子等离子体。随着世界上高能物理实验装置的建造与升级，当前实验室中通过重离子碰撞，可以产生夸克胶子等离子体这样的特殊物质。所以，对夸克胶子等离子体的理论研究，对于理解早期宇宙的形成核演化，以及与重离子实验相关联都非常重要。理论计算预言强子物质在高温高密度时将会演化成一种由夸克和胶子组成的退禁闭的态，也就是夸克胶子等离子体。夸克胶子等离子体存在于早期宇宙，所以对夸克胶子等离子体的研究对了解早期宇宙非常重要。有力的证据证明夸克胶子等离子体可以在LHC和RHIC的原子核碰撞实验中产生。其中重强子（至少包括一个重夸克）对研究夸克胶子等离子体的性质有着重要的意义。因为它在碰撞早期产生，并且参与了体系演化的全过程。在本项目中，我们重点研究了重强子和夸克胶子等离子体性质的关系。首先研究这些强子和夸克胶子等离子体的相互作用，然后将该研究结果和输运理论相结合，得到了实验可观测量的预言值。通过对比理论计算的值和实验观测数据，对对夸克胶子等离子体的性质有更清楚的认识。