A Realistic Pattern of Lepton Mixing and Masses from S4 and CP

TL;DR

This paper proposes a supersymmetric model with S4 x Z3 and CP symmetries that predicts lepton mixing angles, phases, and neutrino mass ordering with minimal parameters, aligning well with experimental data.

Contribution

The model introduces a novel symmetry-breaking pattern that predicts lepton mixing parameters and neutrino masses with only a few parameters, including the reactor angle and CP phases.

Findings

Predicts maximal atmospheric mixing and trivial Majorana phases.

Neutrino masses are normally ordered with a specific mass scale.

Subleading corrections are small, maintaining the model's predictions.

Abstract

We present a supersymmetric model with the flavour symmetry S4 x Z3 and a CP symmetry which are broken to a Z3 subgroup of the flavour symmetry in the charged lepton sector and to Z2 x CP (x Z3) in the neutrino one at leading order. This model implements an approach, capable of predicting lepton mixing angles and Dirac as well as Majorana phases in terms of one free parameter. This parameter, directly related to the size of the reactor mixing angle theta_{13}, can be naturally of the correct order in our model. Atmospheric mixing is maximal, while sin^2 theta_{12} is larger than 1/3. All three phases are predicted: the Dirac phase is maximal, whereas the two Majorana phases are trivial. The neutrino mass matrix contains only three real parameters at leading order and neutrino masses effectively only depend on two of them. As a consequence, they have to be normally ordered and the absolute neutrino mass scale and the sum of the neutrino masses are predicted. The vacuum of the flavons can be correctly aligned. We study subleading corrections to the leading order results and show that they are small.