Measurable Neutrino Mass Scale in A4 x SU(5)

TL;DR

This paper introduces a supersymmetric A4 x SU(5) model predicting quasi-degenerate neutrinos, linking the effective neutrino mass to the overall mass scale, and providing insights into neutrinoless double beta decay.

Contribution

It develops a novel A4 x SU(5) framework combining type I and type II seesaw mechanisms to naturally produce quasi-degenerate neutrino masses and specific mixing patterns.

Findings

Effective neutrino mass m_ee proportional to neutrino mass scale

Predicted leptonic CP phase delta_MNS approximately 90 degrees

Achieved realistic quark and lepton mass and mixing fits

Abstract

We propose a supersymmetric A4 x SU(5) model of quasi-degenerate neutrinos which predicts the effective neutrino mass m_ee relevant for neutrinoless double beta decay to be proportional to the neutrino mass scale, thereby allowing its determination approximately independently of unknown Majorana phases. Such a natural quasi-degeneracy is achieved by using the A4 (as an example of a non-Abelian family symmetry with real triplet representations) to enforce a type II seesaw contribution to the neutrino mass matrix proportional to the identity. Tri-bimaximal neutrino mixing arises from a type I seesaw contribution via A4 family symmetry and constrained sequential dominance. We perform a numerical fit to the quark and lepton masses and quark mixing where a simple ansatz describing quark CP violation with alpha approximately 90 degrees also leads to the leptonic phase prediction delta_MNS approximately 90 degrees.