Flavour violating lepton decays in low-scale seesaws

TL;DR

This paper provides a comprehensive one-loop calculation of flavour violating lepton decays in the supersymmetric inverse seesaw model, highlighting the importance of considering all contributions for accurate predictions and experimental constraints.

Contribution

It presents the first complete calculation including all SUSY and non-SUSY effects in the low-scale seesaw, revealing potential cancellations and their impact on decay rates.

Findings

Cancellations between contributions can reduce branching ratios by up to tenfold.

Full calculations are essential for accurate interpretation of experimental data.

Ratios of cross-sections can distinguish SUSY from non-SUSY dominance.

Abstract

We present the first complete calculation of flavour violating lepton decays taking into account all supersymmetric (SUSY) and non-SUSY contributions in the context of the supersymmetric inverse seesaw, a specific SUSY low-scale seesaw model. We consider radiative and 3-body lepton decays as well as neutrinoless $\mu-e$ conversion in muonic atoms and perform a full one-loop calculation in the mass basis. Taking CMSSM-like boundary conditions for the soft SUSY breaking parameters, we find that cancellations between different contributions are present in several regions, which might reduce the branching ratios by as much as one order of magnitude. This has important consequences when translating current measurements into constraints and estimating the reach of future experiments, and justifies the use of a full calculation. We also show that the ratio of different cross-sections can discriminate between dominant SUSY or non-SUSY contributions.