Distinguishing models with $\mu \to e $ observables

TL;DR

Upcoming experiments on muon lepton flavor violation could potentially exclude popular TeV-scale models by analyzing their distinct signatures in a comprehensive EFT framework.

Contribution

This paper demonstrates how future muon LFV data can distinguish and potentially rule out specific TeV-scale models using a 12-dimensional Wilson coefficient analysis.

Findings

Upcoming experiments will significantly improve sensitivity to LFV processes.

Different models predict distinct patterns in Wilson coefficient space.

Data can exclude certain models based on their predicted coefficient regions.

Abstract

Upcoming experiments will improve the reach for the lepton flavour violating (LFV) processes $\mu \to e \gamma$, $\mu \to e \bar{e} e$ and $\mu A \to e A$ by orders of magnitude. We investigate whether this upcoming data could rule out some popular TeV-scale LFV models (the type II seesaw, the inverse seesaw and a scalar leptoquark) using a bottom-up EFT approach involving twelve Wilson coefficients that can in principle all be determined by experimental measurements. In this 12-dimensional coefficient space, each model can only predict points in a specific subspace; for instance, flavour change involving singlet electrons is suppressed in the seesaw models, and the leptoquark induces negligible coefficients for 4-lepton scalar operators. Using the fact that none of these models can populate the whole region accessible to upcoming experiments, we show that $\mu \to e$ experiments have the ability to rule them out.