A Grand Unified Supersymmetric Theory of Flavor

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.