RUI: Hadron Structure and Interactions

质子结构的确定对于理解宇宙中的物质非常重要，也是理论核物理学的核心挑战。质子是由被称为夸克、反夸克（夸克的反物质对应物）和胶子的基本物质组成的，但是这些成分对质子性质的贡献方式还没有完全被理解。例如，质子有一种被称为自旋的特性，它被用于医学上的应用，比如核磁共振成像扫描，但是人们不知道夸克和胶子的自旋是如何结合在一起产生质子的自旋的。在这个项目中，PI将使用质子进入双粒子状态波动的新理论模型来描述所产生的夸克和反夸克（质子海）对质子特性的贡献。结果将与费米实验室、杰斐逊实验室、RHIC（相对论重离子对撞机）和其他设施的实验测量结果进行比较。本科生将参与该项目，接受核与粒子物理方面的培训，并获得研究方法和科学传播方面的经验。学生们将在专业会议和更广泛的公众面前展示他们的作品。本项目的科学目标是：(1)将PI根据光前沿摄动理论推导出的新的介子-核子波函数模型与裸质子（无涨落）和涨落状态下产生的介子和重子中的夸克和反夸克的动量分布统计模型相结合，建立质子海中反夸克动量分布的混合模型；（ii）通过包括矢量介子对波动的贡献，扩展这一框架来计算质子海中的自旋分布；（三）研究使用新的介子-核子形式因子在核子弹性电磁和轴向形式因子计算中的影响。费米实验室SeaQuest实验的结果将测试一个混合模型，从而验证介子在促进核子海中的作用。对描述矢量介子涨落的形式体系的扩展，将提供一种新的介子云模型来应对RHIC实验测量的自旋不对称性。形状因子的研究将增加对介子在介子-核子相互作用中的作用的理解。该奖项反映了美国国家科学基金会的法定使命，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。

The determination of proton structure is important for understanding matter in the universe, and a central challenge for theoretical nuclear physics. The proton is constructed from basic building blocks of matter called quarks, antiquarks (antimatter counterparts of the quarks) and gluons, but the ways in which these constituents contribute to the properties of the proton are not completely understood. For example, the proton has a property called spin, which is used in medical applications such as MRI scans, but it is not known how the spins of the quarks and gluons combine to give the spin of the proton. In this project the PI will use new theoretical models of the fluctuation of protons into two-particle states to describe the contributions of quarks and antiquarks created (the proton sea) to the properties of the proton. The results will be compared to experimental measurements from Fermilab, Jefferson Lab, RHIC (the Relativistic Heavy Ion Collider) and other facilities. Undergraduate students will participate in the project, receive training in nuclear and particle physics, and gain experience in research methods and scientific communication. The students will present their work at professional meetings and to the broader public.The scientific goals of this project are: (i) to build a hybrid model for the momentum distributions of the antiquarks in the proton sea by combining a new model for pion-nucleon wave functions, derived by the PI from light-front perturbation theory, with a new statistical model for the momentum distributions of the quarks and antiquarks in the bare proton (no fluctuation) and in the pions and baryons created in the fluctuation states; (ii) to extend this framework to calculate spin distributions in the proton sea by including the contribution of vector mesons to the fluctuations; and (iii) to study the effects of using a new pion-nucleon form factors in calculations of nucleon elastic electromagnetic and axial form factors. The results of the Fermilab SeaQuest experiment will test a hybrid model, and thereby the role of the pion in contributing to the nucleon sea. The extension of the formalism to describe vector meson fluctuations will contribute a new meson cloud model to confront the RHIC experimental measurements of spin asymmetry. The form-factor study will increase the understanding of the role of the pion in pion-nucleon interactions.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.