RUI: Hadronic Structure from Spin Observables in pQCD

原子核由质子和中子组成，这两种粒子属于一种更广泛的粒子——强子。然而，这些强子并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）。这些粒子在强子内部形成一个动力系统，由强核力控制。核物理学研究的一个目标是通过这些可见物质的基本部分的相互作用来理解这种内部结构。特别是，对强子和/或部分子的固有性质（称为自旋）敏感的高能碰撞的分析尤其有用。这些观测结果使我们能够探索强子内部部分的三维运动，以及质子的自旋是如何由其组成部分产生的。这项研究将使我们更好地了解强子结构的这些方面，并支持未来在美国建造的电子-离子对撞机的科学研究。为了培养年轻科学家对核物理子领域的兴趣并训练他们将来从事研究工作，本科生将被纳入该项目的实质性部分。该研究项目将进一步加深我们对部分子固有横向运动和相关性敏感的观测值的了解，这允许在动量空间中对强子进行三维成像。这包括对各种对强子自旋敏感的实验数据进行全局分析，以便使用迭代蒙特卡罗程序提取相关函数，对其内部结构进行编码。然后，这些函数将用于对相对论重离子对撞机（RHIC）、杰斐逊实验室的12-GeV升级（JLab-12）和未来的电子-离子对撞机（EIC）即将进行的测量进行预测。由于需要一个严格的理论形式来解释这样的实验数据，该项目还将通过量子色动力学（QCD）中的高阶计算来巩固自旋可观测物中使用的框架。最后，该项目将研究质子自旋如何从其组成部分产生的某些方面，通过分析这种自旋有多少是由于只携带一小部分质子动量的部分。该研究将把第一性原理的结果作为提取可用于计算其在该区域内自旋的部分函数的输入。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 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 us to explore the 3-dimensional motion of partons inside of hadrons and how the proton's spin arises from its constituent partons. This research will give us better insight into these aspects of hadronic structure as well as support the science of the future Electron-Ion Collider to be built in the United States. Undergraduate students will be included in substantive parts of the project in order to foster the interests of young scientists in the subfield of nuclear physics and train them for future careers in research. This research project will further our knowledge of observables sensitive to parton intrinsic transverse motion and correlations, which allow for a 3-dimensional imaging of hadrons in momentum space. This includes performing a global analysis of data from various experiments sensitive to the spin of hadrons in order to extract the relevant functions, using an iterative Monte Carlo routine, that encode their internal structure. These functions will then be used to make predictions for upcoming measurements at the Relativistic Heavy Ion Collider (RHIC), Jefferson Lab's 12-GeV upgrade (JLab-12), and a future Electron-Ion Collider (EIC). Since a rigorous theoretical formalism is needed in order to interpret such experimental data, this project will also solidify the framework used in spin observables through higher-order calculations within quantum chromodynamics (QCD). The project will lastly investigate certain aspects of how the proton spin arises from its constituent partons by analyzing how much of this spin is due to partons that carry only a small fraction of the proton's momentum. The study will incorporate first principle results as input to the extraction of partonic functions that can be used to calculate their spin in this region.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.