Revisiting Bimaximal Neutrino Mixing in a Model with S4 Discrete Symmetry

TL;DR

This paper develops a supersymmetric S4-based model that naturally reproduces bimaximal neutrino mixing with corrections, explains charged lepton hierarchies, and aligns with neutrino oscillation and leptogenesis data.

Contribution

It introduces a novel S4 x Z4 x U(1)_FN model that naturally realizes bimaximal mixing and charged lepton hierarchies with minimal fine tuning.

Findings

Model reproduces neutrino mixing close to bimaximal with Cabibbo-like corrections.

Achieves charged lepton mass hierarchy within the same framework.

Compatible with leptogenesis and baryon asymmetry constraints.

Abstract

In view of the fact that the data on neutrino mixing are still compatible with a situation where Bimaximal mixing is valid in first approximation and it is then corrected by terms of order of the Cabibbo angle, arising from the diagonalization of the charged lepton masses, we construct a model based on the discrete group S4 where those properties are naturally realized. The model is supersymmetric in 4-dimensions and the complete flavour group is S4 x Z4 x U(1)_FN, which also allows to reproduce the hierarchy of the charged lepton spectrum. The only fine tuning needed in the model is to reproduce the small observed value of r, the ratio between the neutrino mass squared differences. Once the relevant parameters are set to accommodate r then the spectrum of light neutrinos shows a moderate normal hierarchy and is compatible, within large ambiguities, with the constraints from leptogenesis as an explanation of the baryon asymmetry in the Universe.