Hydrogen-Antihydrogen Oscillations, Double Proton Decay, and Grand Unified Theories

Abstract

The $\Delta B=\Delta L=2\mathrm{}$ processes hydrogen-antihydrogen oscillation and $\mathrm{pp}\to e^{+}{e}^{+} or {\mu }^{+}{\mu }^{+}$ (double proton decay) in grand unified theories are examined. Although these reactions are very suppressed in the minimal SU(5) model, their rates may be significantly increased by appending a 50-plet of Higgs scalars. In that case relatively light color sextet and doubly charged colorless scalars might mediate $\mathrm{pp}\to e^{+}{e}^{+} or {\mu }^{+}{\mu }^{+}$ at a rate observable in ongoing proton decay experiments. Consequences of this scenario are discussed.