Enhanced lepton flavour violation in the supersymmetric inverse seesaw

TL;DR

This paper demonstrates that in the supersymmetric inverse seesaw model, Z-penguin diagrams significantly enhance lepton flavour violation signals, especially muon to electron conversion, due to the low seesaw scale and non-decoupling effects.

Contribution

It reveals the dominance of Z-penguin contributions in lepton flavour violation within the supersymmetric inverse seesaw, highlighting their non-decoupling behavior and experimental constraints.

Findings

Z-penguin contributions dominate LFV observables in the inverse seesaw.

Muon to electron conversion rate constrains the model's parameter space.

Z-penguins show non-decoupling behavior similar to LFV Higgs decays.

Abstract

In minimal supersymmetric seesaw models, the contribution to lepton flavour violation from Z-penguins is usually negligible. In this study, we consider the supersymmetric inverse seesaw and show that, in this case, the Z-penguin contribution dominates in several lepton flavour violating observables due to the low scale of the inverse seesaw mechanism. Among the observables considered, we find that the most constraining one is the muon to electron conversion rate which is already restricting the otherwise allowed parameter space of the model. Moreover, in this framework, the Z-penguins exhibit a non-decoupling behaviour, which has previously been noticed in lepton flavour violating Higgs decays.