Lepton Flavor Violation in Models with $A_4$ and $S_4$ Flavor Symmetries

TL;DR

This paper investigates lepton flavor violation processes within $A_4$ and $S_4$ flavor symmetry models, highlighting their potential observability in upcoming experiments and emphasizing the importance of these processes in testing such models.

Contribution

It provides a detailed analysis of LFV processes in $A_4$ and $S_4$ models, especially under inverted hierarchy, and assesses their experimental detectability.

Findings

$ ext{Mu-e}$ conversion in Ti is within next-generation experimental sensitivity.

$ ext{Mu-e}$ conversion in Al is likely observable in significant parameter regions.

$ au$ decay processes are generally below future experimental sensitivity.

Abstract

The lepton flavor violation $\mu\to e\gamma$, $\tau\to e\gamma$, $\tau\to\mu\gamma$, $\mu\to3e$, $\tau\to3e$, $\tau\to3\mu$ and $\mu-e$ conversion in Al and Ti are studied in both the Altarelli-Feruglio $A_4$ model and the $S_4$ model of Ding. The rates of these lepton flavor violation process for the inverted hierarchy neutrino mass spectrum are enhanced considerably by the next to leading order contributions. For both models, we find that the $\mu-e$ conversion in Ti is within the precision of next generation experiments in all the parameter space considered, the $\mu-e$ conversion in Al should be observable at least in a very significant part of the parameter space, whereas $\tau\to e\gamma$, $\tau\to\mu\gamma$, $\tau\to3e$ and $\tau\to3\mu$ are below the expected future sensitivity. The detectability of $\mu\to e\gamma$ and $\mu\to3e$ in near future depends on the models and the neutrino mass spectrum. We suggest that a comprehensive consideration of the lepton flavor violation processes is important to test and distinguish both discrete flavor symmetry models.