Hard Scattering Processes in QCD

QCD 中的硬散射过程

• 批准号: 2110472
• 负责人: Andreas Metz
• 金额: $ 36万
• 依托单位: Temple University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2110472&HistoricalAwards=false
• 关键词: Hard; Scattering; Processes; QCD

Nucleons (protons and neutrons) make up more than 99% of the mass of the visible matter of the Universe. They are composed of quarks and gluons (partons), the fundamental particles of quantum chromodynamics (QCD). The parton structure of the nucleon is encoded in different types of parton distributions (PDFs), which can be extracted from high-energy scattering processes or obtained from first-principles calculations (lattice-QCD). For one crucial PDF, the nucleon transversity, a striking and persistent mismatch exists between results from experiment and lattice-QCD. The PI and his collaborators will revisit and improve the extraction of the transversity from experiment, aiming to obtain state-of-the-art information about the transversity from phenomenology and to find the source of the aforementioned discrepancy. Furthermore, the PI will perform comprehensive calculations in perturbative QCD that are needed to obtain, from lattice-QCD results, two important classes of PDFs that are difficult to address experimentally. The PI will also carefully study the QCD energy momentum tensor, which contains information about fundamental hadron properties like the mass and the spin, as well as pressure and shear distributions. Moreover, the PI will mentor graduate students, conduct outreach activities for high school students and undergraduates, and offer a summer program on hadronic physics for both undergraduate and graduate students.The project deals with three topics in hadronic physics. First, the PI will perform a new fit of the nucleon’s transversity distribution based on data for di-hadron production. After a new leading-order analysis, the transversity will be extracted in a collinear next-to-leading order (NLO) framework. This includes the first-ever NLO calculation, in perturbative QCD, of the relevant di-hadron observables in electron-positron annihilation, lepton-nucleon scattering and proton-proton collisions. The study can shed new light on the longstanding tension between information on the transversity from experimental data and from lattice-QCD. Second, the PI will consider Euclidean parton correlators to enhance our understanding of twist-3 PDFs and generalized parton distributions via lattice-QCD. Specifically, the PI will compute in perturbative QCD the relevant one-loop matching coefficients, which are crucial for relating results from lattice-QCD to the light-cone correlation functions one is interested in. Third, the PI will consider the QCD energy momentum tensor to study the mass decomposition of the pion in QCD, and to explore the pressure as well as the distributions of pressure and shear inside hadrons. A focus will be on properly renormalized operators, an important topic which so far has not received much attention, especially in relation to the pressure and shear distributions.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.

核子（质子和中子）占宇宙可见物质质量的99%以上。 它们由夸克和胶子（部分子）组成，它们是量子色动力学（QCD）的基本粒子。 核子的部分子结构被编码在不同类型的部分子分布（PDF）中，这些分布可以从高能散射过程中提取或从第一性原理计算（格子QCD）中获得。 对于一个关键的PDF，核子的横向性，一个惊人的和持久的不匹配之间存在的实验和晶格QCD的结果。 PI和他的合作者将重新审视和改进从实验中提取的横向性，旨在从现象学中获得关于横向性的最新信息，并找到上述差异的来源。 此外，PI将在微扰QCD中进行全面的计算，这些计算是从格子QCD结果中获得两类重要的PDF所必需的，这两类PDF很难在实验上解决。 PI还将仔细研究QCD能量动量张量，其中包含有关强子基本性质的信息，如质量和自旋，以及压力和剪切分布。 此外，PI还将指导研究生，为高中生和本科生开展外展活动，并为本科生和研究生提供强子物理学暑期课程。该项目涉及强子物理学的三个主题。 首先，PI将根据双强子产生的数据对核子的横向分布进行新的拟合。 在一个新的领导阶分析后，横向性将被提取在一个共线的下一个领导阶（NLO）的框架。 这包括有史以来第一次非线性光学计算，在微扰QCD中，在电子-正电子湮灭，轻子-核子散射和质子-质子碰撞的相关双强子观测值。 这项研究可以为长期存在的来自实验数据和格点QCD的横向信息之间的紧张关系提供新的线索。 第二，PI将考虑欧几里德部分子算符，以增强我们通过格点QCD对扭曲-3 PDF和广义部分子分布的理解。 具体来说，PI将计算微扰QCD中的相关单圈匹配系数，这对于将格点QCD的结果与人们感兴趣的光锥相关函数联系起来至关重要。 第三，PI将考虑QCD能量动量张量来研究QCD中π介子的质量分解，并探索强子内部的压力以及压力和剪切力的分布。 重点将放在适当的重整化算子上，这是一个重要的主题，到目前为止还没有得到太多的关注，特别是在压力和剪切分布方面。该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持的。

项目成果

Simultaneous Extraction of Unpolarized PDFs and Nuclear Effects

• DOI: 10.21468/scipostphysproc.8.098
• 发表时间: 2022-07
• 期刊: SciPost Physics Proceedings
• 作者: C. Cocuzza;A. Metz;N. Sato

The gravitational form factors of the electron in quantum electrodynamics

量子电动力学中电子的引力形状因子

• DOI: 10.1016/j.physletb.2023.137768
• 发表时间: 2023
• 期刊: Physics Letters B
• 影响因子: 4.4
• 作者: Freese, Adam;Metz, Andreas;Pasquini, Barbara;Rodini, Simone
• 通讯作者: Rodini, Simone

First Lattice QCD Study of Proton Twist-3 GPDs

• DOI: 10.22323/1.396.0054
• 发表时间: 2021-12
• 期刊: Proceedings of The 38th International Symposium on Lattice Field Theory — PoS(LATTICE2021)
• 作者: S. Bhattacharya;K. Cichy;M. Constantinou;J. Dodson;A. Metz;Aurora Scapellato;F. Steffens

Energy-momentum tensor form factors in QED

QED 中的能量动量张量形状因子

• DOI: 10.21468/scipostphysproc.8.122
• 发表时间: 2022
• 期刊: Proceedings for the XXVIII International Workshop on Deep-Inelastic Scattering and Related Subjects
• 作者: Rodini, S.;Metz, A.;Pasquini, B.
• 通讯作者: Pasquini, B.

Sea Asymmetry from Polarized W Boson Production

偏振 W 玻色子产生产生的海洋不对称性

• DOI: 10.21468/scipostphysproc.8.025
• 发表时间: 2022
• 期刊: Proceedings for the XXVIII International Workshop on Deep-Inelastic Scattering and Related Subjects
• 作者: Cocuzza, C.;Metz, A.;Sato, N.
• 通讯作者: Sato, N.