SUPERHEAVY SPECTRUM AND SUPERSYMMETRIC GRAND UNIFICATION

We examine in detail the effect of the superheavy particle spectrum on the claim that recent data from CERN LEP are consistent with a SUSY S U(5) grand unified theory (GUT) whose superparticle spectrum is charac terized by a single scale M(S) of approximately 1 TeV, and has three c ouplings unifying at a scale mu = M(V). Using the most recent LEP dete rmination of alpha(s), 0.125+/-0.005, we find that SUSY unification re quires that M(S) < 100 GeV. Larger values of M(S) can be accommodated by assuming that SIGMA, a multiplet transforming as the adjoint of SU( 5), has a mass 8 to 12 orders of magnitude below the GUT scale, with t he GUT scale close to or even above the Planck scale. Larger values of alpha(s), with unification below the Planck scale, may be accommodate d only by breaking the degeneracy of the color octet and weak triplets of the SIGMA multiplet, but this splitting appears in SUSY SU(5) GUT' s only as a gravitational effect in the form of nonrenormalizable oper ators.