RUI: Studies of Nucleon Structure Using Electromagnetic Probes at Jefferson Lab

现在一个公认的事实是，核子、质子和中子是由更基本的粒子——夸克组成的。该基金支持的主要物理项目旨在研究质子的结构。更具体地说，我们在杰斐逊实验室散射质子中的电子来测量质子的电和磁特性。我们的团队通过设计新的实验，建造先进的粒子探测器，开发新的分析和建模软件来参与这些努力。我们通过为本科生和研究生提供有意义的、实质性的项目让学生参与进来。我们小组长期建立的实验计划体现了杰斐逊实验室的主要任务：阐明质子、中子和介子的基本结构。我们的重点是实验，这将进一步我们的理解质子的夸克自旋结构在非摄动状态。杰斐逊实验室最近完成了对12 GeV能量电子束的升级，我们的团队现在准备利用增加的物理范围。我们将继续领导在杰斐逊实验室将质子电磁形状因子比的测量扩展到可能的最高动量转移，并研究核介质中该形状因子比的可能修改。这些实验将为现有的质子结构理论模型提供严格的检验，并将为基于量子色动力学（QCD）的更先进模型的发展提供强大的推动力。

It is now a well-established fact that nucleons, protons and neutrons, are made up of more elementary particles called quarks. The main physics program supported by this grant aims to study of the structure of the proton. More specifically, we scatter electrons from protons at Jefferson Laboratory to measure the electric and magnetic properties of the proton. Our group is involved in these efforts through the design of new experiments, the construction of advanced particle detectors, and the development of novel analysis and modeling software. We involve students by providing meaningful, substantive projects to both undergraduate and graduate students. Our group's long established program of experiments embody Jefferson Lab's primary mission: to elucidate the underlying structure of protons, neutrons, and mesons. We focus on experiments which will further our understanding of the quark spin structure of the proton in the non-perturbative regime. Jefferson Lab has recently completed an upgrade to electron beams of energy 12 GeV, and our group is now poised to take advantage of the increased physics reach. We continue to lead the efforts to extend the measurement of the proton electromagnetic form factor ratio to the highest momentum transfers possible at Jefferson Lab, and also investigate the possible modification of this form factor ratio within the nuclear medium. These experiments will provide severe tests of the available theoretical models of proton structure, and will serve as a strong impetus for the development of more advanced models based upon quantum chromodynamics (QCD).