Hard Probes of Relativistic Heavy Ion Collisions

在极高的温度和密度下，我们每天经历的正常核物质“融化”成所谓的夸克-胶子等离子体（QGP）阶段，由“准自由”夸克和胶子组成，这个阶段被认为在我们的宇宙在大爆炸中诞生后的头10微秒就存在了。这种QGP可以通过将物质加热到1.7亿电子伏特以上的温度来产生。实验上，这是通过两个大核（通常是金或铅）在非常高的能量下碰撞来完成的。由此产生的热而致密的火球预计将在自身压力下膨胀，并冷却下来。QGP的温度、压力、化学势、粘度、扩散系数、声速等性质可以从火球发射的数千个粒子中推断出来，并通过围绕相互作用区域的大型粒子探测器进行检测。这些研究分别在相对论重离子对撞机（RHIC）的PHENIX实验和大型强子对撞机（LHC）的ATLAS实验中进行。提议的研究集中在一组可以通过PHENIX探测器建立在RHIC产生的高密度物质的特性的独家测量上，并研究使用ATLAS探测器在LHC上应用这些测量技术的可能性。具体来说，这种物质的性质将通过测量高能单射流和背靠背射流对（di-jets）来探测。这项提议的研究将提高我们目前对极端条件下物质基本性质的理解，因此对天体物理学和超弦理论等其他领域的研究具有广泛的影响。期望研究生和本科生参与整个课程。PHENIX实验为各级教育提供了多样化的研究课题，以及涉及数百名该领域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.