Flavor symmetry and proton decay

Abstract

We consider a class of SU(5) grand unified models with superheavy fermions as well as the three light families. Mixing of superheavy and light fermions can cause Cabibbo-like suppression of proton decay. In a model with an SO(3) flavor symmetry, the minimal SU(5) prediction m τ= 1 3 m b is preserved, while predictions for m e and m μ are not. Cabibbo favored proton decay modes are p→ πμ and p→Ke, but not p→K μ. The top quark mass is θ; c ( m b m d ) m c ≃ 150 GeV .