Grand Unification and Proton Decay:Prospects For Major Discoveries at The Next Generation Detectors

With coupling unification and neutrino oscillations discovered, proton decay remains the notable missing piece of grand unification, based on the symmetry SU(4)-color. The minimal such unifying symmetry isSO(10). A framework has been developed a few years ago, based on a supersymmetricSO(10) model with a minimal low-dimensional Higgs system, that has some very desirable features. These include: (i) a full resolution of certain generic problems of grand unification, including that of doublet-triplet splitting, in a natural way; and (ii) an analysis of gauge coupling unification in the presence of unification-scale threshold corrections. As a bonus, the latter yields an intriguing inverse correlation between the d=6 (p  e+ pi-zero) and d=5 (p  nu-bar K+) decay amplitudes, which are otherwise unrelated. Together with empirical lower limits on the inverse rates for the two decay modes, such a correlation allows one to derive constrained theoretical upper limits for the same, for any (assumed) spectrum for the supersymmetric partners of the standard model particles. An update of this work in light of constraints on the supersymmetric spectrum from the results of LHC Run I will be presented. The corresponding predicted upper limits for the inverse rates for proton decaying via the two canonical modes mentioned above turn out to be within a factor of ten above the current SuperKamiokande lower limits. Such upper limits in turn present a genuine prospect for discovery of proton decay in the next-generation large underground detectors. The multi-purpose benefits of these detectors coupled to long –baseline neutrino beams will be noted.