Hard Probes of Relativistic Heavy Ion Collisions

在极高的温度和密度下，我们每天所经历的正常核物质“熔化”成所谓的夸克-胶子等离子体(QGP)相，该相由“准自由”夸克和胶子组成，据信在我们的宇宙在大爆炸中诞生后的头10微秒内就存在。这种QGP可以通过加热温度高于170毫安电子伏特的物质而产生。在实验上，这是通过以非常高的能量碰撞两个大原子核(通常是金或铅)来实现的。由此产生的又热又密的火球预计会在自身的压力下膨胀，并冷却下来。QGP的性质，如其温度、压力、化学势、粘度、扩散系数、声速等，可以从火球发出的数千个粒子中推断出来，并由相互作用区域周围的大型粒子探测器检测到。这些研究分别是在相对论重离子对撞机(RHIC)的PHENIX实验中进行的，以及计划在大型强子对撞机(LHC)上进行的ATLAS实验。拟议的研究集中在一系列独家测量上，这些测量可以确定RHIC通过PHENIX探测器产生的高密度物质的性质，并调查使用ATLAS探测器在大型强子对撞机上应用这些测量技术的可能性。具体地说，这种物质的性质将通过测量高能单喷流和背靠背喷流对(双喷流)来探测。这项拟议的研究将改善我们目前对极端条件下物质基本性质的理解，因此对其他领域的努力具有广泛的影响，如天体物理学和超弦理论。预计研究生和本科生将在整个项目中参与。PHENIX实验为各级教育提供了一系列多样化的研究课题，以及一个涉及该领域数百名科学家之间互动的良好工作环境，以及在编程、硬件、领导力和学术方面的独特职业发展机会。

At extremely high temperature and density, the normal nuclear matter we experience every day ``melts'' into the so called Quark-gluon plasma (QGP) phase consisting of ``quasi-free'' quarks and gluons, a phase believed to have existed during the first 10 microseconds after our universe was born in the Big Bang. This QGP can be created by heating matter above a temperature of 170 millon electron volts. Experimentally, this is done by colliding two large nuclei (typically Gold or Lead) at very high energy. The resulting hot and dense fireball is expected to expand under its own pressure, and cool down. Properties of the QGP such as its temperature, pressure, chemical potential, viscosity, diffusion coefficient, speed of sound, etc. can be deduced from thousands of particles emitted from the fireball and detected with large scale particle detectors surrounding the interaction region. Such studies are being carried out in the PHENIX experiment at the Relativistic Heavy-ion Collider (RHIC) and planned for the ATLAS experiment at the Large Hadron Collider (LHC), respectively. The proposed research is focused on a set of exclusive measurements that can establish the properties of the high density matter created at RHIC via the PHENIX detector, and on investigating the possibilities of applying these measurement techniques at LHC using the ATLAS detector. Specifically, the properties of this matter will be probed via measurements of high energy single jets and back-to-back jet pairs (di-jets). The proposed research will improve our present understanding of the fundamental nature of the matter under extreme conditions, and therefore has a broad impact on other fields of endeavor such as astrophysics and super-string theories. Participation by graduate students and undergraduate students is expected throughout the program. The PHENIX experiment provide a diverse array of research topics at all levels of education, as well as an excellent working environment involving interactions between hundreds of scientists in the field, and unique opportunities for career development in programming, hardware, leadership and academics.