Fundamental Symmetries using Lattice QCD with the Gradient Flow

即使粒子物理学标准模型（SM）取得了非凡的成功，在宇宙中观察到的某些现象对我们所知的生命产生了深远的影响，例如物质-反物质不对称，层次问题以及暗物质和暗能量的存在，仍然无法解释。因此，对这些现象的任何物理描述都需要一个超越标准模型（BSM）的理论，同时包含标准模型及其与普通物质相关的预测。对造成物质-反物质不对称的对称性破缺敏感的物理量是中子和质子等粒子的电偶极矩。PI将研究超越标准模型的理论对宇宙中物质-反物质不对称性的影响，计算这些理论引起的质子和中子的电偶极矩。除了研究标准模型之外的理论对宇宙中观察到的物质-反物质不对称性所起的作用，这是粒子和核物理学中最大的未回答的问题之一，PI将指导一名从事这项研究的学生。这个项目使用一种新方法，基于所谓的梯度流，用于确定与夸克和强theta-CP破坏相关的关键BSM矩阵元素的量子色动力学（QCD）分量。这组矩阵元素影响了对核子和原子核内电偶极矩（EDM）的理解（BSM物理学的一个关键特征），它们的确定将为从未来的低能量，高强度实验测量中提取BSM观测值奠定基础。梯度流的使用将规避上述矩阵元素的确定所带来的一些巨大挑战，引入新的尺度，流动时间，这将减轻计算中存在的分歧。此外，梯度流非常适合于在格点上的QCD计算。格点QCD是目前唯一可靠的、理论上合理的非微扰QCD计算方法。PI开发的新方法非常适合于计算所有CP破坏对核子和轻核EDM的贡献。该项目开发的大多数工具和技术都是传统方法的替代品，可以很容易地应用于其他有助于暗物质候选者研究的矩阵元计算。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。

Even with the extraordinary success of the the Standard Model of Particle Physics (SM), certain phenomena observed in the Universe that have profound consequences to life as we know it, such as the matter-antimatter asymmetry, the hierarchy problem, and the existence of dark matter and dark energy, remain unexplained. Therefore any physical description of such phenomena requires a theory that goes beyond the Standard Model (BSM), while at the same time encompassing the Standard Model and its predictions related to ordinary matter. A physical quantity sensitive to the symmetry breaking responsible for the matter-antimatter asymmetry is the electric dipole moment (EDM) of particles such as neutron and proton. The PI will study the impact of theories beyond the Standard Model on the matter-antimatter asymmetry in the universe, calculating the electric dipole moments of protons and neutrons induced by such theories. In addition to investigating the role played by theories beyond the Standard Model on the observed matter-antimatter asymmetry in the universe, which is one of the biggest unanswered questions in particle and nuclear physics, the PI will mentor a student engaged in this research.This project uses a new method, based on the so-called gradient flow, for the determination of the Quantum Chromodynamics (QCD) component of key BSM matrix elements related to quark and strong theta-CP violations. This set of matrix elements impacts the understanding of electric dipole moments (EDMs) within nucleons and nuclei (a key signature of BSM physics) and their determination will lay the foundation for extraction of BSM observables from future low-energy, high-intensity experimental measurements. The use of the gradient flow will circumvent some of the big challenges posed by the determination of the above-mentioned matrix elements, introducing a new scale, the flow time, that will mitigate divergences present in the calculations. Additionally the gradient flow is perfectly suited to be adopted on QCD calculations on the lattice. Lattice QCD is, as today, the only robust and theoretically sound approach to non-perturbative QCD calculations. The new method the PI has developed is ideally suited to calculate all the CP-violating contributions to the EDM of nucleons and light nuclei. Most of the tools and technique developed in this project are alternative to traditional methods and can be easily applied to other matrix element calculations contributing to the study of dark matter candidates.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.