Viable low-scale model with universal and inverse seesaw mechanisms

A E Cárcamo Hernández,Juan Marchant González,U J Saldaña-Salazar

doi:10.1103/physrevd.100.035024

Abstract

We formulate a viable low-scale seesaw model, where the masses for the standard model (SM) charged fermions lighter than the top quark emerge from a universal seesaw mechanism mediated by charged vectorlike fermions. The small light active neutrino masses are produced from an inverse seesaw mechanism mediated by right-handed Majorana neutrinos. Our model is based on the $A_{4} $ family symmetry, supplemented by cyclic symmetries, whose spontaneous breaking produces the observed pattern of SM fermion masses and mixings. The model can accommodate the muon and electron anomalous magnetic dipole moments and predicts strongly suppressed $\mu\rightarrow e\gamma $ and $\tau\rightarrow \mu \gamma $ decay rates, but allows a $\tau \rightarrow e\gamma $ decay within the reach of the forthcoming experiments.

Highlights

The standard model (SM) has offered us a theoretical framework with great experimental success
II, despite the presence of several heavy vectorlike charged exotic leptons that trigger the universal seesaw mechanism, we assume that all of them have masses of the same order of magnitude, implying the need of implementing a Froggatt-Nielsen mechanism to generate the SM charged lepton mass hierarchy. Such a Froggatt-Nielsen mechanism is implemented by considering nonrenormalizable operators involving gauge singlet scalar fields charged under the discrete symmetries of the model, whose spontaneous breaking is crucial to yield the SM charged lepton mass hierarchy
In this work we propose a low-scale seesaw model with extended scalar and fermion sectors, consistent with the current pattern of SM fermion masses and mixings

Summary

INTRODUCTION

The standard model (SM) has offered us a theoretical framework with great experimental success. In regards to the neutrino sector, to generate the small light active neutrino masses that satisfy Eq (2), we consider an inverse seesaw mechanism II, despite the presence of several heavy vectorlike charged exotic leptons that trigger the universal seesaw mechanism, we assume that all of them have masses of the same order of magnitude, implying the need of implementing a Froggatt-Nielsen mechanism to generate the SM charged lepton mass hierarchy Such a Froggatt-Nielsen mechanism is implemented by considering nonrenormalizable operators involving gauge singlet scalar fields charged under the discrete symmetries of the model, whose spontaneous breaking is crucial to yield the SM charged lepton mass hierarchy.

THE MODEL

QUARK MASSES AND MIXINGS

PHENOMENOLOGY ð44Þ j

Charged LFV decays

CONCLUSIONS