Relativistic Heavy Ion Collision Studies at the LHC and RHIC

这是一个为期三年的项目，主要是进行相对论重离子碰撞实验。 该方案的目标有三个方面。 第一个目标是研究重原子核在可达到的最高能量下碰撞产生的极致密物质的时空特性。 夸克物质被认为是在这些碰撞中产生的，其特征是大量的夸克和胶子，正常物质的微观成分，如质子和中子。 第二个目标是研究量子色动力学（QCD）的体相结构，QCD被认为是描述夸克和胶子之间相互作用的正确理论。 这将通过将碰撞条件改变为较低能量来实现，以便探测正常物质和夸克物质之间的过渡。 第三个目标是利用为研究重离子碰撞中的体物理而开发的工具，并将其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，如流体动力学流动。 如果我们最初关于质子-质子碰撞中的这种流动的报道在这些更高的能量下得到证实，这就提出了关于流动的性质以及这些碰撞的初始状态的性质的重要问题。 在本项目中，将在布鲁克海文国家实验室（BNL）的相对论重离子对撞机（RHIC）上研究相对论重离子碰撞，并在日内瓦欧洲核子研究中心的大型强子对撞机（LHC）上研究铅-铅碰撞。 RHIC于2000年夏天开始提供束流，是目前运行的最高能量重离子加速器。 为了寻找夸克物质相变发生的特征，必须研究碰撞中产生的粒子的性质，例如可以检测到的每种类型的粒子动量和多重性（例如π介子，K介子，质子和更多的奇异粒子）。 这将在RHIC使用星星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感兴趣的粒子进行采样。 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（使用两粒子干涉测量法），碰撞中达到的温度（从粒子动量分布）和奇异粒子的产生，如奇怪的重子。 此外，在大型强子对撞机上利用ALICE实验进行的更高能量的质子-质子和铅-铅碰撞研究将于2010年4月开始。 LHC将提供比RHIC高30倍的质心能量，即宇宙射线能量，与RHIC的结果进行有用的比较。 该项目在教育、技术和计算机领域对社会产生了更广泛的影响。 由于本科生、研究生和博士后研究人员将在本项目中发挥关键作用，因此将向这些群体提供如何在大型合作中开展研究和解决一般问题的技能方面的培训。 该研究需要大规模计算，以获得和分析万亿次和万亿字节规模的数据，并将开发新的信息科学方法，如计算网格系统，这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.