A Grand Unified Supersymmetric Theory of Flavor

TL;DR

This paper develops a grand unified supersymmetric model with a hierarchical U(2) flavor symmetry breaking, explaining fermion mass hierarchies and flavor mixing with minimal parameters and making specific predictions for mixing angles and masses.

Contribution

It introduces a unified SU(5) framework with a U(2) flavor symmetry that constrains flavor interactions and reduces free parameters, providing a predictive model for fermion masses and mixings.

Findings

Predicts two CKM mixing angles and two fermion masses.

Determines six flavor mixing matrices with a single free parameter.

Explains fermion mass hierarchies without small Yukawa parameters.

Abstract

A grand unified $SU(5)$ theory is constructed with a hierarchical breaking of a $U(2)$ flavor symmetry. The small parameters of the squark and slepton mass matrices, necessary to solve the supersymmetric flavor-changing problem, and the inter-generational quark and lepton mass hierarchies are both generated from the $U(2)$ symmetry breaking parameters. The flavor interactions of the theory are tightly constrained, with just 10 free real parameters for both the fermion and scalar sectors. All but one of the 8 small fermion mass ratios, and all of the 3 small Cabibbo-Kobayashi-Maskawa mixing angles, can be understood without introducing small dimensionless Yukawa parameters. Predictions are made for 2 of the Cabibbo-Kobayashi-Maskawa mixing angles and for 2 of the fermion masses. The six flavor mixing matrices which appear at the neutralino vertices, and which in general are arbitrary unitary matrices, are determined in terms of just a single free parameter.