B-L Violating Proton Decay Modes and New Baryogenesis Scenario in SO(10)

We show that grand unified theories based on SO(10) generate quite naturally baryon number violating dimension seven operators that violate B-L, and lead to novel nucleon decay modes such as n --> e(-) K+, e(-) pi(+) and p --> nu pi(+). We find that in two-step breaking schemes of nonsupersymmetric SO(10), the partial lifetimes for these modes can be within reach of experiments. The interactions responsible for these decay modes also provide a new way to understand the origin of matter in the Universe via the decays of grand unified theory ( GUT) scale scalar bosons of SO(10). Their ( B-L)-violating nature guarantees that the GUT scale induced baryon asymmetry is not washed out by the electroweak sphaleron interactions. In minimal SO(10) models this asymmetry is closely tied to the masses of quarks, leptons and the neutrinos.