Mapping the Structure of Hadrons with Lattice QCD

了解可见物质的内部结构是核物理的一个重要研究领域。原子核的基本组成部分，质子和中子，是由基本夸克和胶子组成的，由强相互作用理论，量子色动力学（QCD）控制。在过去的60年里，我们的知识有了很大的进步，但仍有许多谜团：这些夸克和胶子是如何构成复合粒子的质量的？他们如何贡献他们的旋转？一个少了一个夸克的π介子，质量怎么会低10倍呢？许多实验设施也在竞相回答这些问题，如杰斐逊实验室加速器12-GeV计划和计划中的电子离子对撞机。这些实验将推进核子和其他粒子的层析成像。与此同时，高性能计算允许直接模拟QCD，提供有关难以通过实验获得的方面的信息。格点QCD（LQCD）是一种利用超级计算机直接模拟四维时空格点QCD的理论方法。使用这种技术，强子系统的性质可以从第一性原理（即从基本的夸克和胶子自由度）进行研究，具有完全可控的数值和系统的不确定性。在过去的十年中，有显着的进展，在开发有效的算法产生的QCD配置和工具，从LQCD相关函数提取相关信息的合奏。在某些情况下，LQCD计算已经达到了一个水平，他们不仅补充，而且指导实验计划。目前正在进行两个主要的研究方向。首先是提供精确的LQCD计算的核子耦合和时刻的晶格系统学的全面研究，包括多个晶格间距和体积，直接在物理π质量。将精确的LQCD输入与正在进行和即将进行的精确低能实验相结合，可以帮助为新物理学设定极限。第二个方向是用准和伪PDF方法研究非单线态强子结构。重点是在大多数全球拟合中最大的理论不确定性之一，奇异-反奇异对称性假设和核子和介子的胶子结构。该奖项反映了NSF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。

Understanding the innermost structure of visible matter is an important research area in nuclear physics. The basic building blocks of the atomic nucleus, protons and neutrons, are composed of elementary quark and gluon constituents governed by the theory of the strong interaction, quantum chromodynamics (QCD). Our knowledge has advanced greatly over the last six decades but many puzzles remain: How do these quarks and gluons make up the masses of composite particles? How do they contribute to their spin? How can a pion, composed of one fewer quark, have mass roughly 10 times lower? Many experimental facilities are also racing to answer these questions, such as the Jefferson Lab accelerator 12-GeV program and the planned Electron-Ion Collider. These experiments will advance the tomography of nucleons and other particles. At the same time, high-performance computing allows the direct simulation of QCD directly, providing information about aspects that are hard to access via experiments. Lattice QCD (LQCD) is a theoretical method to directly simulate QCD on four-dimensional spacetime lattices using supercomputers. Using this technique, the properties of hadronic systems can be studied from first principles (that is, from the underlying quark and gluon degrees of freedom) with fully controllable numerical and systematic uncertainties. In the past decade, there has been significant progress in the development of efficient algorithms for generating ensembles of QCD configurations and tools for extracting relevant information from LQCD correlation functions. In some cases, LQCD calculations have reached a level where they not only complement, but also guide experimental programs. Two main research directions are being pursued. The first is to provide precision LQCD calculations of nucleon couplings and moments with full studies of lattice systematics, including multiple lattice spacings and volumes, directly at physical pion mass. Combining precision LQCD inputs with ongoing and upcoming precision low-energy experiments can help set limits for new physics. The second direction is to investigate non-singlet hadron structure using quasi- and pseudo-PDF methods. Focus is on one of the biggest theoretical uncertainties in most global fits, the assumption of strange-antistrange symmetry and the gluon structure of nucleons and mesons.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.