Relativistic Heavy Ion Collision Studies at the LHC and RHIC

这是一个为期三年的项目，主要进行相对论重离子碰撞实验。这个项目的目标有三个方面。第一个目标是研究在可达到的最高能量的重核碰撞中产生的极高密度物质的时空特性。据信，夸克物质是在这些碰撞中产生的，其特征是大量夸克和胶子，以及质子和中子等正常物质的微观组成部分。第二个目标是研究量子色动力学（QCD）的体相结构，这被认为是描述夸克和胶子之间相互作用的正确理论。这将通过改变碰撞的条件以降低能量来实现，以便探测正常物质和夸克物质之间的转变。第三个目标是将用于研究重离子碰撞体物理的工具应用于类似能量的质子-质子碰撞。我们将特别关注这些碰撞中的集体行为，比如流体动力流动。如果我们关于质子-质子碰撞中这种流动的最初报告在这些更高能量下得到证实，这就提出了关于流动性质的重要问题，以及这些碰撞的初始状态的性质。在目前的项目中，相对论重离子碰撞将在布鲁克海文国家实验室（BNL）的相对论重离子对撞机（RHIC）和日内瓦欧洲核子研究中心（CERN）的大型强子对撞机（LHC）上进行金-金碰撞研究。RHIC于2000年夏天开始发射粒子束，是目前运行中能量最高的重离子加速器。为了寻找已经发生了向夸克物质相变的特征，人们必须研究碰撞中产生的粒子的性质，例如粒子动量和每种类型可以检测到的多样性（例如介子、介子、质子和更多的外来粒子）。这将在RHIC使用STAR实验的大型接收探测器完成，它可以在每次碰撞中对大多数有趣的粒子进行采样。以这种方式获得的信息可以用来确定，例如，相互作用区域的物理大小（使用双粒子干涉测量法），在碰撞中达到的温度（从粒子动量分布）和奇异粒子的产生，如奇异重子。此外，在2010年4月之前，在大型强子对撞机上，利用ALICE实验对更高能量的质子-质子和铅-铅碰撞进行研究。大型强子对撞机将提供比RHIC高30倍的质心能量，即宇宙射线能量，这使得与RHIC的结果进行有用的比较。这个项目在教育、技术和计算领域对社会有更广泛的影响。由于本科生、研究生和博士后研究人员将在该项目中发挥关键作用，因此将向这些群体提供如何开展大型合作研究和一般问题解决技能的培训。这项研究需要大规模的计算来获取和分析teraflop和tb规模的数据，而信息科学的新方法，如计算网格系统，将被开发出来，可以提高整个社会的计算能力。

This is a three-year project primarily to carry out experiments with relativistic heavy ion collisions. The goals for this program are three-fold. The first goal is to study the space-time properties of the extremely dense matter created in collisions between heavy nuclei at the highest achievable energies. It is believed that Quark Matter is created in these collisions, characterized by a large collection of quarks and gluons, the microscopic components of normal matter such as protons and neutrons. The second goal is to study the bulk phase structure of Quantum Chromodynamics (QCD), believed to be the correct theory to describe interactions between quarks and gluons. This will be achieved by varying the conditions of the collision to lower energies in order to probe the transition(s) between normal matter and Quark Matter. The third goal is to take the tools developed to study bulk physics in heavy ion collisions and apply them to proton-proton collisions at similar energies. We will look particularly for collective behavior, such as hydrodynamic flow, in these collisions. If our initial reports of such flow in proton-proton collisions are confirmed at these higher energies, this raises important issues about the nature of flow, and the nature of the initial state of these collisions. In the present project, relativistic heavy ion collisions will be studied with gold-gold collisions at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL), and with lead-lead collisions at the Large Hadron Collider (LHC) at CERN in Geneva. RHIC, which started delivering beams in Summer 2000, is the highest energy heavy ion accelerator now in operation. In order to look for signatures that a phase transition to Quark Matter has taken place, one must study the properties of the particles produced in the collisions, such as particle momenta and multiplicities of each type that can be detected (e.g. pions, kaons, protons, and more exotic particles). This will be done at RHIC using the large acceptance detectors of the STAR experiment, which can sample most of the interesting particles per collision. The information obtained in this way can be used to determine, for example, the physical size of the interaction region (using two-particle interferometry), the temperatures reached in the collisions (from particle momentum distributions) and exotic particle production such as strange baryons. In addition, studies of proton-proton and lead-lead collisions at even higher energies at the LHC with the ALICE experiment will begin by April 2010. The LHC will provide beams 30 times higher in center-of-mass energy than RHIC, i.e. cosmic ray energies, making for a useful comparison with results from RHIC. There are broader impacts to society of this project in the areas of education, technology and computing. Since undergraduate students, graduate students and postdoctoral researchers will play key roles in this project, training will be provided to these groups in how to carry out research in large collaborations and in general problem solving skills. This research requires large-scale computing in order to acquire and analyze data on the teraflop and terabyte scale, and new methods in information science, such as computing grid systems, will be developed which can enhance the computing power of society as a whole.