Saturation Physics: NLO Precision and Quasi Collectivity

量子色动力学（QCD）的研究，描述了夸克和胶子（原子核的最基本成分）之间的基本相互作用的理论，代表了核物理学中一个强烈探索的领域。特别是，QCD被要求描述物质在极端温度、压力和密度条件下的行为，并且需要精确的计算来比较定量实验和理论。在这种情况下，PI和他的合作者将开发精确的计算方法，以允许搜索在高能质子-质子和铅-质子碰撞中预测发生的奇异形式的物质，目前在瑞士欧洲核子研究组织（CERN）的大型强子对撞机（LHC）进行研究。该项目还包括教育和外联活动：PI将为东北部大学的研究生组织一个讲习班。将为参与本研究的教师组织高能/重离子物理方面的迷你课程。在非常高的能量下，强相互作用粒子（强子）的结构被认为经历了质的转变。它们不像含有几个夸克和胶子的稀释物体，而更像一滴被胶子密集填充的饱和液体。这必然导致高能碰撞中最终态的特征非常不同。定性描述这种行为的理论是微扰饱和或彩色玻璃凝聚（CGC）。在目前的LHC能量下，人们预计这个新阶段已经达到了。事实上，许多观测表明，在质子-质子和质子-铅碰撞的最终状态中，存在某种集体或准集体行为，特别是当产生的粒子数量大于平均水平时。在这种情况下，PI和他的合作者将为系统改进当前饱和效应计算范式的程序的发展做出贡献。这首先涉及到高能演化方程的系统恢复程序，即所谓的JIMWLK方程，目的是将其稳定在次领先阶（NLO）。然后将恢复的演化应用于在NLO一致计算的各种强子观测。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。

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.