SO(10) GRAND UNIFICATION WITH A LOW-ENERGY SU(2)R-SYMMETRY-BREAKING SCALE M(R)

Contrary to commonly held belief, we show that one can obtain a low va lue for M(R), the SU(2)R breaking scale, in grand unification theories based on SO(10). This possibility emerges in the supersymmetric versi on of SO(10) with a judicious choice of Higgs content. The unification scale is found to be consistent with the constraint from proton decay . This result is first explicitly demonstrated using the one-loop reno rmalization group equations, and then a full two-loop analysis is carr ied out.