Nuclear $\mu-e$ conversion via Lorentz and CPT violation

TL;DR

This paper explores how nuclear mu-e conversion experiments can be used to detect Lorentz and CPT violation, providing new bounds on quark-lepton operators within the Standard-Model Extension framework.

Contribution

It introduces the first bounds on quark-lepton operators related to Lorentz and CPT violation from nuclear mu-e conversion data, and discusses potential improvements from future experiments.

Findings

Established first bounds on relevant operators from SINDRUM II data

Analyzed Lorentz and CPT-violating contributions in mu-e conversion

Discussed prospects for improved constraints with upcoming experiments

Abstract

One of the three common experimental channels searching for charged lepton flavor violation (CLFV) via $\mu-e$ conversion involves first capturing the muon on a nuclear target. This channel provides a unique opportunity to constrain four-point quark-lepton operators that may contribute to CLFV, in addition to the electromagnetic operators that can also be accessed in the other channels. We investigate the leading Lorentz- and CPT-violating contributions for nuclear $\mu-e$ conversion experiments within the Standard-Model Extension and obtain the first bounds on the relevant quark-lepton operators using the results of the SINDRUM II experiment; we also consider possibilities for improved constraints from upcoming experiments.