Nucleon Decay in GUT and Non-GUT SUSY Models

Abstract

I first emphasize the importance of searching for nucleon decay in the context of supersymmetric models. The status of minimal SUSY SU(5) model is reviewed, which can be definitively ruled out by a combination of superKamiokande and LEP-2 experiments. Non-minimal models may provide some suppression in the nucleon decay rates, but there is still a good chance for superKamiokande. I point out that the operators suppressed even by the Planck-scale are too large. We need a suppression mechanism for the operators at the level of $10^{-7}$, and the mechanism, I argue, may well be a flavor symmetry. A particular example predicts $p \rightarrow K^0 e^+$ to be the dominant mode which does not arise in GUT models.