Nucleon Structure and Hadronization Beyond the Collinear Leading Twist Parton Model

核子是构成我们的物质的主要组成部分，它是如何从基本的强相互作用基本粒子夸克和胶子中构建出来的，这是核物理学中一个长期存在的问题。本计画将借由研究核子中夸克与胶子的相关性与三维动量分布来探讨此一问题。为此，实验上可测量的可观测量在理论上分析了可以在美国的设施，如杰斐逊实验室（JLab），相对论重离子对撞机（RHIC）和未来的电子-离子对撞机（EIC）以及世界各地的其他设施实现的核反应。这项研究所基于的微观理论是量子色动力学（QCD）。这个项目感兴趣的几个观测值需要光束或目标的自旋极化，甚至是产生的末态粒子。这些自旋观测量的理论分析需要的方法和精确的计算，超越了非极化核反应的共同标准理论方法。该项目的主要目标是对微扰QCD中的核子结构以及部分子碎裂进行理论研究。它的目的是研究高能核过程的可观测量超出标准的领先扭曲共线因式分解方法。重点是两个关键领域：1）在共线twist-3形式下的单包容核过程中的横自旋效应。2)极化和非极化质子碰撞中横动量相关的胶子分布。这些研究的结果将对JLab，RHIC，大型强子对撞机（LHC）和未来EIC的实验计划产生直接影响。 该项目的主要目标是：（一）在共线扭曲-3形式主义框架内对单包容核反应中的横向自旋极化观测值进行理论分析：目标是对横向自旋观测值进行次领先（NLO）计算，并研究三部分子相关函数的尺度依赖性。此外，PI将在JLab和EIC研究轻子-核子碰撞中光子终态的可行性; ii）在横向动量相关（TMD）分解中探索核子的胶子结构：用TMD方法分析质子核中各种胶子感生自旋观测值，在RHIC上的质子与处于末态的重夸克偶素的碰撞被认为是包括TMD演化的实施在内的。这个奖项反映了美国国家科学基金会的基金会的使命是履行其法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

It has been a long-standing question in nuclear physics of how the nucleon, the main building block of the matter that we are made of, is built from fundamental strongly-interacting elementary particles, the quarks and gluons. This project will address this question by studying correlations and 3-dimensional momentum distributions of quarks and gluons in the nucleon. To this end experimentally measurable observables are theoretically analyzed for nuclear reactions that can be realized at US-based facilities like the Jefferson Laboratory (JLab), the Relativistic Heavy Ion Collider (RHIC), and the future Electron-Ion Collider (EIC), as well as other facilities worldwide. The underlying microscopic theory on which this research is based is Quantum Chromodynamics (QCD). Several observables that are of interest for this project need spin polarization of the beam or the target, or even the produced final state particles. The theoretical analyses of those spin observables require methods and precision calculations that go beyond the common standard theoretical approaches for unpolarized nuclear reactions. The PI will mentor graduate students and include an undergraduate student in this research program.The main goal of this project is a theoretical investigation of the nucleon structure as well as parton fragmentation within perturbative QCD. It is intended to study observables of high-energy nuclear processes beyond the standard leading twist collinear factorization approach. The focus is on two key areas: 1) Transverse spin effects in single-inclusive nuclear processes within the collinear twist-3 formalism. 2) Transverse momentum dependent gluon distributions in polarized and unpolarized proton collisions. The outcome of these studies will have direct impact for experimental programs at JLab, RHIC, the Large Hadron Collider (LHC), and a future EIC. The main thrusts of the project are: i) Theoretical analyses of transverse spin-polarized observables in single-inclusive nuclear reactions in the framework of collinear twist-3 formalism: The goal is to perform next-to-leading (NLO) calculations for transverse-spin observables and to study the scale dependence of three-parton correlation functions. Furthermore, the PI will investigate the feasibility of photonic final state in lepton-nucleon collisions at JLab and EIC; ii) Exploration of the gluonic substructure of the nucleon within Transverse Momentum Dependent (TMD) factorization: TMD analyses of various gluon-induced spin observables in proton-proton collisions at RHIC with Heavy Quarkonia in the final state are considered including implementation of TMD evolution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.