RUI: Hadronic Structure from Spin Observables in pQCD

原子核由质子和中子组成，质子和中子是更广泛的强子粒子类别的一部分。然而，这些强子不是物质的基本形式，因为它们是由其他粒子组成的，即夸克和胶子(统称为部分子)。这些部分粒子在强子内部形成了一个受强核力支配的动力系统。核物理研究的一个目标是通过这些部件的相互作用来了解这种内部结构，这些部件是可见物质的基本部件。特别是，对对强子和/或部分子的一种称为自旋的本征性质敏感的高能碰撞的分析特别有用。这些观测可以探索强子内部部子的三维运动，以及质子的自旋是如何从其组成的部分子中产生的。这项研究更好地洞察了强子结构的这些方面，并支持了未来将在美国建造的电子-离子对撞机的科学。该项目的实质性部分包括本科生，目的是培养年轻科学家对核物理这一子领域的兴趣，并培训他们从事未来的研究工作。这一研究项目进一步加深了我们对对部分子固有横向运动和关联敏感的可观测性的了解，这些关联允许在动量空间中对强子进行三维成像，以及质子自旋的起源。这包括对各种实验的数据进行贝叶斯蒙特卡罗全局分析，包括电子-正电子、电子-质子和质子-质子的单强子和双强子终态的碰撞，对部子和/或强子的自旋敏感，并严格纳入胶子辐射效应。还对未来在不同实验设备上的测量进行了预测。此外，人们需要一个强有力的理论形式主义来解释实验数据。这个项目通过对一些反应的次要顺序计算，巩固了在双强子自旋可观测中使用的框架。最后，这个项目开发了一种机制来确定携带质子动量的一小部分x的部分粒子产生了多少自旋，这是质子自旋如何从其组成部分动态产生的一个关键但约束很差的部分。这一奖项反映了NSF的法定使命，并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，被认为值得支持。

The nucleus of an atom is made up of protons and neutrons, which are a part of a broader category of particles called hadrons. However, these hadrons are not a fundamental form of matter since they are composed of other particles, namely, quarks and gluons (collectively called partons). The partons form a dynamical system inside of hadrons that is governed by the strong nuclear force. A goal of nuclear physics research is to understand this internal structure through the interactions of these partons, the elementary pieces of visible matter. In particular, the analysis of high-energy collisions sensitive to an intrinsic property, called spin, of hadrons and/or partons is especially useful. These observables allow the exploration of the 3-dimensional motion of partons inside of hadrons and how the proton's spin arises from its constituent partons. This research gives better insight into these aspects of hadronic structure as well as supports the science of the future Electron-Ion Collider to be built in the United States. Undergraduate students are included in substantive parts of the project in order to foster the interests of young scientists in this subfield of nuclear physics and train them for future careers in research. This research project furthers our knowledge of observables sensitive to parton intrinsic transverse motion and correlations, which allow for a 3-dimensional imaging of hadrons in momentum space, as well as the origin of the proton's spin. This includes performing Bayesian Monte Carlo global analyses of data from various experiments, including electron-positron, electron-proton, and proton-proton collisions for single-hadron and dihadron finals states, sensitive to the spin of partons and/or hadrons, with a rigorous incorporation of gluon radiation effects. Predictions are also made for future measurements at different experimental facilities. In addition, one needs a robust theoretical formalism in order to interpret experimental data. This project solidifies the framework used in dihadron spin observables through next-to-leading order calculations of some reactions. Lastly, this project develops the machinery to determine how much spin arises from partons that carry a small fraction x of the proton’s momentum, which is a crucial, yet poorly-constrained, piece of how the proton’s spin dynamically arises from its constituent partons.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.