PROTON DECAY AND RELATED PROCESSES MODELS WITH GAUGED BARYON NUMBER

In unification models based on SU(15) or SU(16), baryon number is part of the gauge symmetry, broken spontaneously. In such models, we discu ss various scenarios of important baryon-number-violating processes su ch as proton decay and neutron-antineutron oscillation. Our analysis d epends on the effective operator method, and covers many variations of symmetry breaking, including different intermediate groups and differ ent Higgs-boson content. We discuss processes mediated by gauge bosons and Higgs bosons in parallel. We show how accidental global or discre te symmetries present in the full gauge invariant Lagrangian restrict baryon-number-violating processes in these models. In all cases we fin d that baryon-number-violating interactions are sufficiently suppresse d to allow grand unification at energies much lower than the usual 10( 16) GeV.