Differential Measures of Parton Energy Loss in the Quark Gluon Plasma Using Photon Jet Correlations

众所周知，质子和中子是由称为夸克和胶子的较小成分组成的。在使用两束重原子核的碰撞中，会形成一种新的物质状态，称为夸克-胶子等离子体(QGP)。这个项目将回答有关QGP的基本问题，例如物质如何从质子和中子的集合转变为自由状态，在这种状态下，夸克和胶子可以畅通无阻地在太空中传播，就像他们在大爆炸后的原始物质汤中所做的那样。该项目的目标是通过使用夸克的硬碰撞来探测这种高温的核介质，从而在更短的尺度上解析QGP的性质，从而探测QGP的内部工作原理。这项研究将在位于布鲁克海文国家实验室的相对论重离子对撞机(STAR)的螺线管跟踪器上进行。粒子喷注是在重离子碰撞的最初阶段形成的，当时两个夸克或胶子有一个硬散射，在这个过程中，它们被朝相反的方向踢，大致垂直于重离子粒子束。在这种相互作用中被踢出的夸克和胶子将穿过介质，相互作用并向其损失能量。然后，它们被碎片和强子化成一束粒子，可以由恒星上的探测器测量到。具体地说，这项工作将集中在与RHIC最高能量处的即时光子-喷注关联相关的可观测性上。与其他观测结果相比，这具有优势，即由于动量守恒和光子不与夸克胶子等离子体相互作用的事实，喷流的横向动量是明确已知的。这些测量对于理解夸克-胶子相互作用理论模型的关键特征的温度和能量依赖性是必要的。

It is a well-established fact that protons and neutrons are made up of smaller constituents called quarks and gluons. In collisions using two beams of heavy nuclei, a new state of matter is formed, called the quark-gluon plasma (QGP). This project will answer fundamental questions about the QGP, such as how matter is transformed from a collection of protons and neutrons to a free state where quarks and gluons can travel through space unhindered, much like they did in the primordial soup of matter following the Big Bang. The goal of the project is to probe the inner workings of the QGP by resolving its properties at much shorter length scales by using hard collisions of quarks to probe this hot nuclear medium. This research will be performed at the Solenoidal Tracker at the Relativistic Heavy Ion Collider (STAR), which is located at Brookhaven National Laboratory. Particle jets are formed in the very initial stages of the heavy ion collision, when two quarks or gluons have a hard scattering in which they are kicked in opposite directions from one another and roughly perpendicular to beam of heavy ion particles. The quarks and gluons that are kicked out in such an interaction will travel through the medium, interacting and losing energy to it. They then fragment and hadronize into a spray of particles that can be measured by the detectors at STAR. Specifically, the effort will concentrate on observables related to prompt photon-jet correlations at the top energies at RHIC. This has the advantage over other observables that the transverse momentum of the jet is explicitly known due to both conservation of momentum, and the fact that the photon does not interact with the Quark Gluon Plasma. These measures will be necessary to understand the temperature and energy dependence of key features of theoretical models of the quark-gluon interactions.