Limits on Lepton Flavor Violation from \mu-e-conversion

TL;DR

This paper analyzes the constraints on lepton flavor violating e conversion in nuclei caused by e-e contact interactions, updating bounds and exploring implications for collider searches.

Contribution

It reevaluates hadronic parameters and provides updated bounds on e-e contact interactions from e conversion experiments, including new theoretical insights.

Findings

Updated upper bounds on e-e contact interaction scales.

Comparison of e conversion limits with other LFV processes.

Discussion on LHC search prospects for these interactions.

Abstract

We revisit the status of Lepton Flavor Violating (LFV) \mu e qq contact interactions from the view point of \mu - e -conversion in nuclei. We consider their contribution to this LFV process via the two mechanisms on the hadronic level: direct nucleon and meson exchange ones. In the former case the quarks are embedded directly into the nucleons while in the latter in mesons which then interact with nucleons in a nucleus. We revise and in some cases reevaluate the hadronic parameters relevant for both mechanisms and calculate the contribution of the above mentioned contact interactions in coherent \mu - e -conversion in various nuclei. Then we update the existing upper bounds and also derive new ones for the scales of the \mu e qq contact interactions from the experimental limits on the capture rates of \mu - e -conversion. We compare these limits with the ones derived in the literature from other LFV processes and comment on the prospects of LHC searches related to the contact \mu e qq interactions.