RUI: Study of the Nucleon Structure Using Deeply Virtual Compton Scattering at Jefferson Lab.

RUI：杰斐逊实验室使用深度虚拟康普顿散射研究核子结构。

• 批准号: 1812151
• 负责人: Angela Biselli
• 金额: $ 14.84万
• 依托单位: Fairfield University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-15 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1812151&HistoricalAwards=false
• 关键词: RUI; Study; Nucleon; Structure; Using

Understanding the structure of the nucleon has been the focus of many scientists for decades. Over the past 40 years there has been a tremendous theoretical and experimental advancement that brought us to the discovery of quarks as fundamental bricks of matter and the laws that govern their interactions. The generalized parton distributions (GPDs) are theoretical tools used to describe hadrons (particles that are made from quarks and gluons) in terms of their constituents. These distributions give fully correlated quark information in both coordinate and momentum space, allowing access to crucial properties such as the angular momentum distribution of quarks in the nucleon and explaining how quarks contribute to the overall properties of nucleons such as their electric and axial charge. This project will focus on experiments at Thomas Jefferson National Accelerator Facility (Jefferson Lab) in Newport News, VA using the recently upgraded Continuous Electron Beam Accelerator Facility (CEBAF) large acceptance spectrometer (CLAS12). Jefferson lab with its "intermediate" energies is a unique facility to explore the region sensitive to the valence quarks, and the large acceptance CLAS12 detector will allow the extraction of GPDs over large kinematic ranges. The PI of this proposal is a co-spokesperson of three experiments aimed to extraction of GPDs. The PI will take an active role in the data taking at Jefferson Lab and will contribute to the data reduction and analysis. Undergraduate students will be involved in this project and in addition to gaining experience in data analysis in particle physics, they will develop broader skills, such as coding and statistics.The cleanest way to access GPDs is via deeply virtual Compton scattering (DVCS), where the virtual photon interacts with a single quark of the nucleon radiating a real photon. At leading twist, the soft process is described by four chiral-even GPDs: the quark-helicity independent, H, E and the quark helicity dependent H-tilde and E-tilde. The focus of this project is to measure target and beam asymmetries and cross sections for the DVCS with proton and neutron targets. These observables on different nucleons have unique sensitivity to a subset of the four GPDs, and their simultaneous determination allows for a comprehensive extraction of GPDs for the proton and neutron and flavor decomposition. In September 2018, the unpolarized proton target run will start, providing a significant amount of additional production data. Experiments on the neutron target and the polarized proton target are expected to run in the next three years. Fairfield University will contribute to the physics analysis and other aspects of the data reduction such as quality tests, calibration and software development. In addition to the work on the new data, as it becomes available, Fairfield University will continue to complete simulation work in preparation to the upcoming experiments to study the optimal configuration of the detector.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.

几十年来，了解核子的结构一直是许多科学家关注的焦点。在过去的 40 年里，理论和实验取得了巨大的进步，使我们发现了作为物质基本组成部分的夸克以及支配它们相互作用的定律。广义部分子分布 (GPD) 是用于描述强子（由夸克和胶子组成的粒子）成分的理论工具。 这些分布在坐标和动量空间中提供了完全相关的夸克信息，允许访问关键属性，例如核子中夸克的角动量分布，并解释夸克如何影响核子的整体属性，例如它们的电荷和轴向电荷。该项目将重点在弗吉尼亚州纽波特纽斯的托马斯杰斐逊国家加速器设施（杰斐逊实验室）进行实验，使用最近升级的连续电子束加速器设施（CEBAF）大接收光谱仪（CLAS12）。具有“中间”能量的杰斐逊实验室是探索对价夸克敏感区域的独特设施，并且大接受度 CLAS12 探测器将允许在大运动学范围内提取 GPD。该提案的 PI 是三个旨在提取 GPD 的实验的联合发言人。 PI 将在杰斐逊实验室的数据采集中发挥积极作用，并将为数据缩减和分析做出贡献。本科生将参与该项目，除了获得粒子物理数据分析经验外，他们还将培养更广泛的技能，例如编码和统计。访问 GPD 最干净的方法是通过深度虚拟康普顿散射 (DVCS)，其中虚拟光子与辐射真实光子的核子的单个夸克相互作用。在前旋处，软过程由四个手性偶 GPD 描述：夸克螺旋度无关的 H、E 以及夸克螺旋度相关的 H 代号和 E 代号。该项目的重点是测量质子和中子靶标的 DVCS 的靶标和束流不对称性以及横截面。 不同核子上的这些可观测值对四个 GPD 的子集具有独特的敏感性，并且它们的同时测定允许对质子和中子以及风味分解的 GPD 进行全面提取。 2018 年 9 月，非极化质子目标运行将开始，提供大量额外的生产数据。中子靶和极化质子靶的实验预计将在未来三年内进行。费尔菲尔德大学将致力于物理分析和数据缩减的其他方面，例如质量测试、校准和软件开发。除了对新数据的研究之外，费尔菲尔德大学还将继续完成模拟工作，为即将进行的实验做好准备，以研究探测器的最佳配置。该奖项反映了 NSF 的法定使命，并被认为是值得的通过使用基金会的智力优势和更广泛的影响审查标准进行评估来提供支持。