Fundamental Symmetries using Lattice QCD with the Gradient Flow

即使粒子物理标准模型(SM)取得了非凡的成功，但在宇宙中观察到的某些对我们所知的生命具有深远影响的现象，如物质-反物质不对称、等级问题以及暗物质和暗能量的存在，仍然没有得到解释。因此，对这种现象的任何物理描述都需要一种超越标准模型(BSM)的理论，同时还包括标准模型及其与普通物质相关的预测。引起物质-反物质不对称性的一个对对称性破缺敏感的物理量是粒子的电偶极矩(EDM)，如中子和质子。PI将研究标准模型以外的理论对宇宙中物质-反物质不对称的影响，计算由这些理论引起的质子和中子的电偶极矩。除了调查超越标准模型的理论在宇宙中观察到的物质-反物质不对称上所起的作用，这是粒子和核物理中最大的悬而未决的问题之一，PI还将指导一名从事这项研究的学生。这个项目使用了一种基于所谓的梯度流的新方法，来确定与夸克和强theta-CP违反有关的关键BSM矩阵元素的量子色动力学(QCD)分量。这组矩阵元素影响对核子和原子核内电偶极矩(EDM)(BSM物理学的一个关键特征)的理解，它们的确定将为从未来低能量、高强度的实验测量中提取BSM可观测值奠定基础。梯度流的使用将绕过上述矩阵元素的确定带来的一些重大挑战，引入了一个新的标度，即流动时间，这将减少计算中存在的分歧。此外，梯度流非常适合于在晶格上进行QCD计算。和今天一样，格子QCD是唯一稳健且理论上可靠的非微扰QCD计算方法。PI发展的新方法非常适合于计算核子和轻核的所有违反CP的电火花加工贡献。在这个项目中开发的大多数工具和技术都是传统方法的替代方法，可以很容易地应用于其他有助于研究暗物质候选者的矩阵元素计算。该奖项反映了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。

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.