The Common, the Rare, and the Unseen: precision theory for precision experiments

Particle physics is at a crossroads. The largest collider ever built so far has found no evidence for physics beyond the Standard Model leaving us with major open problems such as the absence of antimatter in our universe and the origin of nonzero neutrino masses. While plans for new colliders with extreme collision energies are being pursued, an alternative way to find new clues is through low-energy precision experiments that can detect subtle quantum effects from beyond-the-Standard-Model physics. The experimental prospects are great, but their interpretation requires high-precision theoretical calculations of particle physics effects on complex systems such as neutrons, atomic nuclei, and molecules. My goal is to develop new theoretical tools based on effective field theory to greatly improve the theoretical accuracy of the most promising high-precision observables. I will focus on superallowed beta decay measurements (the Common), extremely rare double-weak decays of atoms (the Rare), and yet-to-be-discovered neutrinoless double beta decay and permanent electric dipole moments (the UNSeen). These observables are targeted by an intense worldwide experimental program and have the potential to unravel the nature of neutrino mass, to break the Standard Model pattern of quark mixing, and to find the origin of the universal matter-antimatter asymmetry. Doing so requires the new tools and methods developed in this proposal to improve the theoretical accuracy to record levels and to connect low-energy experiments to mysteries in high-energy particle physics and cosmology.