Evan Rule

Rule
Evan Rule,
N3AS & Univ. of California, Berkeley
Dec. 13th, 2022

About me:
I am currently a postdoctoral fellow with the Network for Neutrinos, Nuclear Astrophysics, and Symmetries. I earned my PhD in Physics from the University of California, Berkeley in 2022 under the supervision of Wick Haxton. My research is primarily focused on tests of fundamental symmetries in nuclear systems, especially searches for new physics in the form of lepton flavor violating muon-to-electron conversion. More broadly, I am interested in the development of effective theories for nuclear problems, including efforts to connect many-body nuclear physics to quantum chromodynamics.

Seminar Title:
Muon-to-Electron Conversion: From the top-down and the bottom-up

Seminar Date:
Dec. 13th, 2022

Abstract:
Limits on the charged lepton flavor violating (CLFV) process of μ→e conversion are expected to improve by four orders of magnitude due to the next generation of experiments, Mu2e at Fermilab and COMET at J-PARC. While the kinematics of the decay of a trapped muon are ideal for detecting a signal of CLFV, the intervening nuclear physics presents a significant roadblock to the interpretation of experimental results. We report on two directions of recent progress: First, we describe how a limited class of scalar-mediated quark-level interactions can be reduced to the nuclear scale, yielding predictions for CLFV branching ratios with well-understood uncertainties and allowing one to place rigorous constraints on certain candidate UV models. Second, we introduce an effective theory of μ→e conversion formulated directly at the nuclear scale, which factorizes the nuclear physics from the CLFV leptonic physics, sequestering the latter quantity into unknown low-energy constants (LECs) that are probed directly by experiments. Utilizing state-of-the-art shell-model calculations of nuclear response functions, we discuss how a program of μ→e conversion measurements on different targets—selected for their nuclear ground-state properties—could constrain the unknown LECs.

References: https://arxiv.org/abs/2203.09547, https://arxiv.org/abs/2208.07945, https://arxiv.org/abs/2109.13503