Comprehensive Investigation of Ultra-Relativistic Heavy Ion Collisions at RHIC and the LHC

在正常的核物质中，构成质子和中子的夸克和胶子被永久地限制在强子中。当温度达到数万亿开氏度时，这就不再正确了。在这种极高的温度下，空间充满了热产生的强子，以至于单个强子不再能保持其约束的完整性。实际上，普通的核物质“熔化”并释放出夸克和胶子。被释放的夸克和胶子形成了一种新的物质状态，称为夸克-胶子等离子体（QGP）。在过去的20年里，欧洲核子研究中心和美国布鲁克海文国家实验室的相对论重离子对撞机一直在碰撞重原子核以产生和表征QGP。到目前为止，实验已经积累了大量的证据，证明人们所追求的QGP确实是在相对论重离子碰撞中产生的。然而，在实验证据中发现的许多性质是非常令人惊讶的。例如，这种有史以来最热、密度最大的物质也可能是有史以来观测到的相互作用最强的系统之一，它的流动比超流体氦更理想！世界上许多研究小组对这些性质进行了深入的理论研究。然而，尽管欧洲核子研究中心的大型强子对撞机在前所未有的高碰撞能量下开始积累大量的新数据，但仍有许多重要的难题有待理论解决。要全面理解重离子碰撞中的QGP，需要大量的理论武器库。这包括经典的Yang-Mills理论、3+1D相对论粘性流体动力学和强子分子动力学模拟。这是一个雄心勃勃的目标，但在这一点上，我是世界上少数几个能够整理所有必要工具的人之一。在这个建议中，我建议用我和我的学生可以使用的所有理论工具来进行重离子碰撞中QGP的全面表征。

In normal nuclear matter, quarks and gluons which constitute protons and neutrons, are permanently confined inside the hadrons. When temperature reaches trillions of kelvin, this is no longer true. At these extremely high temperatures, space is so packed with thermally produced hadrons that an individual hadron can no longer maintain the integrity of its confinement. In effect, ordinary nuclear matter "melts'' and releases the quarks and gluons. The liberated quarks and gluons then form a new state of matter called the Quark-Gluon Plasma (QGP). This extreme state of matter existed in nature only about a microsecond after the Big-Bang.For the past 2 decades, relativistic heavy ion colliders at CERN in Europe and at Brookhaven National Laboratory in the US have been colliding heavy nuclei to create and characterize QGP. By now, the experiments have accumulated an ample amount of evidence that the sought-after QGP is indeed being created in relativistic heavy ion collisions. Many of the properties found in the experimental evidence were, however, highly surprising. For example, this hottest and densest matter ever created may also be one of the most strongly interacting systems ever observed, flowing more ideally than the superfluid Helium! There have been intense theoretical investigations on these properties by many groups in the world. However, there are still many important puzzles that await theoretical resolution even as the LHC at CERN is beginning to accumulate a tremendous amount of new data at an unprecedentedly high colliding energy.A comprehensive understanding of QGP in heavy ion collisions calls for a remarkable range of theoretical arsenals. This includes classical Yang-Mills theory, relativistic viscous hydrodynamics in 3+1D and a hadronic molecular dynamics simulations. This is an ambitious goal, but at this point, I am one of the very few in the world who is capable of marshaling all the necessary tools. In this proposal, I propose to carry out comprehensive characterization of QGP in heavy ion collisions with all the theoretical tools I and my students can employ.