Lepton mixing and charged lepton flavour violation from inverse seesaw with non-degenerate heavy states

TL;DR

This paper explores an inverse seesaw model with non-degenerate heavy states, analyzing its implications for lepton mixing and charged lepton flavor violation, and assessing experimental constraints and future sensitivities.

Contribution

It introduces a flavor symmetry-based inverse seesaw model with non-degenerate heavy states and studies its phenomenological implications for lepton flavor violation.

Findings

Current bounds do not strongly constrain the model.

Upcoming experiments will significantly impact the parameter space.

The model accommodates observed lepton mixing angles.

Abstract

We analyse an inverse seesaw scenario with 3+3 gauge singlets. The flavour structure is determined by a flavour symmetry, Delta (3 n^2) or Delta (6 n^2), n integer, and CP and their residual groups among charged leptons and the neutral states. For the latter, the Dirac mass matrix of the gauge singlets carries all non-trivial flavour structure. Consequently, the heavy sterile states form three pseudo-Dirac pairs which have in general distinct masses. We discuss the signal strength of different charged lepton flavour violating processes. Ensuring that the lepton mixing angles can be accommodated at the 3 sigma level or better, we find that the current bounds on the branching ratios of mu -> e gamma, mu -> 3 e, tau -> l gamma and tau -> 3 l, l=e, mu, as well as the rate of mu-e conversion in nuclei do not strongly constrain the considered parameter space, while the limits expected from the upcoming experiments Mu3E, COMET and Mu2e will have a relevant impact.