Embedding A4 into SU(3)xU(1) flavor symmetry: Large neutrino mixing and fermion mass hierarchy in SO(10) GUT

TL;DR

This paper proposes a grand unified flavor and gauge theory combining SU(3)xU(1) flavor symmetry with SO(10) GUT to explain fermion mass hierarchy and large lepton mixing angles through symmetry breaking patterns.

Contribution

It introduces a novel model where dynamical and explicit symmetry breaking patterns explain fermion hierarchies and mixing angles within a unified SO(10) GUT framework.

Findings

Dynamical breaking of SU(3)xU(1) explains mass hierarchy.

Explicit breaking to A4 leads to tribimaximal mixing.

Model naturally accounts for neutrino masses and mixing angles.

Abstract

We present a common explanation of the fermion mass hierarchy and the large lepton mixing angles in the context of a grand unified flavor and gauge theory (GUTF). Our starting point is a SU(3)xU(1) flavor symmetry and a SO(10) GUT, a basic ingredient of our theory which plays a major role is that two different breaking pattern of the flavor symmetry are at work. On one side, the dynamical breaking of SU(3)xU(1) flavor symmetry into U(2)xZ_3 explains why one family is much heavier than the others. On the other side, an explicit symmetry breaking of SU(3) into a discrete flavor symmetry leads to the observed tribimaximal mixing for the leptons. We write an explicit model where this discrete symmetry group is A4. Naturalness of the charged fermion mass hierarchy appears as a consequence of the continuous SU(3) flavor symmetry. Moreover, the same discrete A4-GUT invariant operators are the root of the large lepton mixing, small Cabibbo angle, and neutrino masses.