Fermion Masses in SUSY GUTs

Abstract

We discuss the fermion mass problem in SUSY GUTs, including such ideas as texture zeroes, and Georgi-Jarlskog textures. We focus on a specific supersymmetric model based on the gauge group $SU(4)\otimes SU(2)_L \otimes SU(2)_R$. In this model the gauge group is broken to that of the standard model at $10^{16}$ GeV, and supersymmetry is broken at low-energy. The model may be regarded as a ``surrogate SUSY GUT'', and has several advantages over the $SU(5)$ and $SO(10)$ SUSY GUTs, such as the absence of the doublet-triplet splitting problem, and a simpler Higgs sector which does not involve any large Higgs representations. The model predicts full quadruple Yukawa unification (top-bottom-tau-tau neutrino), leading to the prediction of large top mass and $\tan \beta$. An operator analysis leads to schemes where the strange and down mass are predicted, and $|V_{ub}|>0.004$.