Proton decays in an SO(10) grand unified theory

The lifetime and branching ratios of the proton and (bound) neutron are calculated in an SO(10) grand unified theory by taking into account the form-factor effects due to the finite sizes of the nucleons and mesons. In our approach there is an arbitrary parameter M sub(D)/M sub(E). For M sub(D)/M sub(E) > 1 the lifetime of the proton is predicted to be shorter than the experimental lower bound and the predicted value of the Weinberg angle is too small. For M sub(D)/M sub(E) <= 1/2 the predicted lifetime and branching ratios are nearly equal to those in the SU(5) symmetric limit. (author)