Saturation Physics: NLO Precision and Quasi Collectivity

量子色动力学(QCD)是描述夸克和胶子之间的基本相互作用的理论，夸克和胶子是原子核的最基本成分，它的研究代表了核物理中一个激烈的研究领域。特别是，QCD被用来描述物质在温度、压力和密度等极端条件下的行为，需要精确的计算来定量比较实验和理论。在这种情况下，PI和他的合作者将开发准确的计算方法，从而能够搜索预计将在高能质子-质子和铅-质子碰撞中出现的奇异物质形式，目前瑞士欧洲核研究组织(CERN)的大型强子对撞机(LHC)正在研究这种物质。该项目还包括教育和外联活动：国际和平协会将为东北大学的研究生组织一次讲习班。将为参与这项研究的教师组织关于高能/重离子物理方面的小型课程。在非常高的能量下，强相互作用粒子(强子)的结构被认为经历了质的转变。它们应该更像一滴稠密充满胶子的饱和液体，而不是含有几个夸克和胶子的稀释物。这必然会导致高能碰撞中终态的截然不同的特征。定性描述这一行为的理论是微扰饱和或彩色玻璃凝聚(CGC)。在目前的大型强子对撞机能量下，人们预计这一新阶段已经实现。事实上，许多观测指出，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超过平均水平时，存在某种集体或准集体行为。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例的程序开发做出贡献。这包括首先，系统地恢复高能演化方程，即所谓的JIMWLK方程，以便将其稳定在次前级(NLO)。然后，恢复的演化将被应用于在NLO一致计算的各种强子可观测性。此外，PI还将深入研究初始CGC态的结构在多大程度上可以导致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.