Supersymmetry, local horizontal unification, and a solution to the flavor puzzle

TL;DR

This paper presents a gauge model with local horizontal symmetries that addresses the supersymmetric flavor problem, explains fermion mass hierarchies, and fits neutrino data, with testable predictions for rare decays.

Contribution

It introduces a realistic SU(2)_H x U(1)_H gauge model that solves the supersymmetric flavor problem and explains fermion hierarchies, linking the U(1)_H to string theory.

Findings

The model naturally explains quark mass hierarchies and mixing angles.

It accommodates solar and atmospheric neutrino data.

It predicts observable rare decay    if correct.

Abstract

Supersymmetric gauge models with local horizontal symmetries are known to generate large flavor changing neutral current effects induced by supersymmetry breaking D-terms. We show how the presence of a U(1) gauge symmetry solves this problem. We then construct a realistic gauge model with SU(2)_H x U(1)_H as the local horizontal symmetry and suggest that the U(1)_H factor may be identified with the anomalous U(1) induced by string compactification. This model explains the observed hierarchies among the quark masses and mixing angles, accommodates naturally the solar and atmospheric neutrino data, and provides simultaneously a solution to the supersymmetric flavor problem. The model can be excluded if the rare decay \mu --> e \gamma is not observed in the current round of experiments.