Lepton flavor violation in low-scale seesaw models: SUSY and non-SUSY contributions

TL;DR

This paper investigates lepton flavor violation in low-scale inverse seesaw models, considering both SUSY and non-SUSY contributions, revealing cancellation effects that impact experimental interpretations and potential to distinguish contribution sources.

Contribution

It provides a comprehensive analysis including all contributions to lepton flavor violation in inverse seesaw models, highlighting the importance of cancellations and offering methods to identify dominant mechanisms.

Findings

Cancellations can reduce LFV rates by an order of magnitude.

Ratios of decay branching ratios can distinguish SUSY from non-SUSY contributions.

Results impact interpretation of current and future LFV experimental data.

Abstract

Taking the supersymmetric inverse seesaw mechanism as the explanation for neutrino oscillation data, we investigate charged lepton flavor violation in radiative and 3-body lepton decays as well as in neutrinoless $\mu-e$ conversion in muonic atoms. In contrast to former studies, we take into account all possible contributions: supersymmetric as well as non-supersymmetric. We take CMSSM-like boundary conditions for the soft supersymmetry breaking parameters. We find several regions where cancellations between various contributions exist, reducing the lepton flavor violating rates by an order of magnitude compared to the case where only the dominant contribution is taken into account. This is in particular important for the correct interpretation of existing data as well as for estimating the reach of near future experiments where the sensitivity will be improved by one to two orders of magnitude. Moreover, we demonstrate that ratios like BR($\tau\to 3 \mu$)/BR($\tau\to \mu e^+ e^-$) can be used to determine whether the supersymmetric contributions dominate over the $W^\pm$ and $H^\pm$ contributions or vice versa.