Three-Body Amplitudes from Lattice QCD

宇宙中已知物质的形成是由强大的力量造成的，但具体的形成机制仍然是个谜。强力将原子核中的核子(质子和中子)束缚在一起，核子的性质在最先进的加速器设施中进行研究，如托马斯·杰斐逊国家加速器设施。本项目的目的是利用晶格QCD弥合实验和理论计算之间的差距。由于目前经典计算机的局限性，格子QCD计算通常是在一个小的立方体中进行，而不是在无限大的空间中进行。这个项目提供了从前者到后者的转换，以便QCD的基本计算可以与自然相提并论。PI和他的学生将专注于包含三个相互作用的粒子的系统的性质。为了帮助培养一支多样化的、具有全球竞争力的STEM劳动力队伍，外联部分致力于开发量子力学(QM)计算方面的材料和依赖时间的QM问题的动画。对于三个粒子的有限体积效应，人们知之甚少。在这个项目中，PI和他的学生将开发和应用三体方法来将晶格QCD结果映射到物理世界，并帮助回答有关激发介子和重子性质的QCD预测的基本问题。为此，一元性原理被有效地用作构造三个或更多粒子振幅的指导原则。对以前工作的概念升级涉及到引入更多耦合通道和对半整数自旋的扩展。三体动力学不仅在理论上是困难的，在现象学方面也是困难的。因此，将发展无限体积的三体振幅，并将其与互补努力中的实验进行比较，例如罗珀共振及其多通道三体动力学，或A1(1260)轴介子的各种衰变通道。计划对GW群在两个不同的介子质量下的新格子QCD结果进行扩展分析，这将允许绘制出A1(1260)轴介子的手征轨迹。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。

Strong forces are responsible for the formation of known matter in the Universe, but the detailed mechanisms of how this happens remain a mystery. Strong forces bind nucleons (protons and neutrons) together in atomic nuclei, and the properties of the nucleons are studied at state-of-the-art accelerator facilities such as the Thomas Jefferson National Accelerator Facility. This project aims at closing the gap between experiment and theoretical calculations using lattice QCD. Due to current limitations of classical computers Lattice QCD calculations are performed in a small cubic volume instead of infinite space. This project provides the translation from the former to the latter, so that fundamental calculations of QCD can be compared to Nature. The PI and his students will focus on properties of systems involving three particles interacting with each other. To help develop a diverse, globally competitive STEM workforce, the outreach component is dedicated to developing material for computational aspects of quantum mechanics (QM) and animations of time-dependent QM problems. Finite-volume effects for the case of three particles are poorly understood. In this project, the PI and his students will develop and apply three-body methods to map lattice QCD results to the physical world and to help answer fundamental questions regarding QCD predictions for the properties of excited mesons and baryons. For this, the principle of unitarity is efficiently used as the guiding principle to construct three- or more particle amplitudes. A conceptual upgrade of previous work concerns the introduction of more coupled channels and extensions to half-integer spin. Three-body dynamics is not only difficult on the theory but also on the phenomenology side. Therefore, three-body amplitudes in infinite volume will be developed and compared to experiment in a complementary effort, such as the Roper resonance and its multi-channel three-body dynamics, or the various decay channels of the A1(1260) axial meson. An extended analysis of new lattice QCD results from the GW group at two different pion masses is planned, that will allow to map out the chiral trajectory of the A1(1260) axial meson.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.