Relativistic Heavy-Ion Physics at the University of Rochester

这笔赠款为罗切斯特大学物理和天文学系的相对论重离子小组提供了运营资金。在这笔赠款所涵盖的一年内，我们将利用布鲁克海文国家实验室(BNL)的相对论重离子对撞机(RHIC)的Phobos探测器完成对2001年和2003年收集的数据的分析，并考虑可能的Phobos探测器升级方案。火卫一是观察RHIC原子核碰撞时产生的极端能量密度的四个实验之一。人们相信，在这些碰撞中将形成一种新的物质状态，即所谓的夸克-胶子等离子体(QGP)。火卫一正在寻找这种新的物质状态，它的性质将提供关于非常早期(大爆炸后几微秒)的宇宙状态的重要和新的信息。Phobos的设计目的是以公正的方式研究尽可能多的碰撞，并寻找p-p、p-A和A-A碰撞之间的显著差异。到目前为止收集的数据包括对2001年的Au-Au碰撞，2003年的d-Au碰撞，以及2001和2003年的p-p碰撞的研究。预计QGP只会在Au-Au碰撞中形成，dAu和p-p的研究被用来从Au-Au碰撞中收集的数据中减去“正常”核子-核子物理的贡献。由罗切斯特小组设计和建造的飞行时间阵列通过将火卫一的粒子识别能力大致增加一倍，显著增强了火卫一的物理能力。对于2003年的运行，我们增加了我们阵列的飞行路线，允许使用来识别动量高达4-5GeV/c的粒子。2001年数据的分析几乎完成，而2003年数据的分析才刚刚开始。

This grant provides operating funds for the relativistic heavy-ion group at the Department of Physics and Astronomy at the University of Rochester. During the year covered by this grant we will complete the analysis of the data collected in 2001 and 2003 with the PHOBOS detector at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) and consider possible upgrade options for the PHOBOS detector. PHOBOS is one of the four experiments looking at the extreme energy densities that are created when nuclei collide at RHIC. It is believed that a new state of matter, the so-called quark-gluon plasma (QGP), will be formed in these collisions. PHOBOS is looking for this new state of matter, and its properties will provide important and new information about the state of the very early universe (a few microseconds after the Big Bang). PHOBOS was designed to study as many collisions as possible, in an unbiased way, and to search for significant differences between p+p, p+A, and A+A collisions. The data collected sofar inlcudes studies of Au+Au collisions in 2001, d+Au in 2003, and p+p in 2001 and 2003. It is expected that the QGP will only be formed in the Au+Au collisions, and the studies of d+Au and p+p are used to subtract the contribution of "normal" nucleon-nucleon physics from the data collected in Au+Au collisions. The time-of-flight array, designed and constructed by the Rochester group, significantly enhances the physics capabilities of PHOBOS, by roughly doubling its particle identification capabilities. For the 2003 run we have increased the flight path of our arrays, allowing use to identify particles up to momenta of around 4 - 5 GeV/c. The analysis of the 2001 data is almost completed, and the analysis of the 2003 data is just getting started.