Saturation Physics: NLO Precision and Quasi Collectivity

量子色动力学（QCD）是描述夸克和胶子（原子核的最基本组成部分）之间基本相互作用的理论，它的研究代表了核物理学中一个激烈的研究领域。特别是，QCD被要求描述物质在温度，压力和密度的极端条件下的行为，并且需要精确的计算来定量地比较实验和理论。在这种情况下，PI和他的合作者将开发精确的计算方法，允许搜索预测在瑞士欧洲核研究组织（CERN）的大型强子对撞机（LHC）研究的高能质子-质子和铅-质子碰撞中发生的奇异形式的物质。该项目还包括教育和外联活动：公共信息机构将为东北部各大学的研究生举办一次讲习班。将为参与这项研究的教员组织关于高能/重离子物理学方面的小型课程，在非常高的能量下，强相互作用粒子（强子）的结构据信经历了质的转变。它们不应该是含有几个夸克和胶子的稀释物体，而应该更像一滴充满胶子的饱和液体。这必然导致高能碰撞中的末态具有非常不同的特性。定性描述这种行为的理论是微扰饱和或彩色玻璃冷凝物（CGC）。在目前的LHC能量下，人们预计这个新阶段已经实现。事实上，许多观测结果表明，在质子-质子和质子-铅碰撞的最终状态下，特别是当产生的粒子数量大于平均值时，会出现某种集体或准集体行为。在这种情况下，PI和他的合作者将有助于系统地改进饱和效应的当前计算范例的程序的开发。这首先涉及高能演化方程（所谓的JIMWLK方程）中的系统性再确认程序，以便将其稳定在次领先阶（NLO）。然后，将被应用到各种强子观测值一致计算在NLO的图形化的演变。此外，PI将深入研究初始CGC态的结构在多大程度上导致p-p和p-A碰撞产生的态的准集体性。

The study of Quantum Chromodynamics (QCD), the theory describing the fundamental interactions between quarks and gluons, the most fundamental constituents of nuclei, represents an area of intense inquiry in nuclear physics. In particular, QCD is called upon to describe the behavior of matter under extreme conditions of temperature, pressure, and density, and precision calculations are needed to compare quantitatively experiments and theory. In this context, the PI and his collaborators will develop accurate calculational methods that will allow searches of exotic forms of matter predicted to occur in highly energetic proton-proton and lead-proton collisions currently studied at the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) in Switzerland. This project includes also educational and outreach activities: the PI will organize a workshop for graduate students from universities in the North East. Mini-courses on aspects of high energy/heavy ion physics will be organized for faculty involved in this research.At very high energies the structure of strongly interacting particles (hadrons) is believed to undergo a qualitative transition. Instead of dilute objects containing several quarks and gluons, they should rather resemble a drop of saturated liquid densely filled with gluons. This must lead to very different characteristics of final states in high energy collisions. The theory that qualitatively describes this behavior is the perturbative saturation or Color Glass Condensate (CGC). At current LHC energies one expects this new phase to have been already attained. Indeed many observations point to some sort of collective, or quasi collective behavior in the final state of the proton-proton and proton-lead collisions, especially when the number of produced particles is larger than average. In this context, the PI and his collaborators will contribute the development of a program for systematic improvement of current calculational paradigms of saturation effects. This involves first, systematic resummation program in the high-energy evolution equation, the so-called JIMWLK equation in order to stabilize it at next-to-leading order (NLO). The resummed evolution then will be applied to a variety of hadronic observables consistently calculated at NLO. In addition, the PI will study in depth to what extent the structure of initial CGC state can lead to quasi collectivity in the state produced in p-p and p-A collisions.