SU(5) UNIFICATION REVISITED

Model-independent criteria for unification in the SU (5) framework are studied. These are applied to the minimal supersymmetric standard model and to the standard model with a split 45 Higgs representation. Although the former is consistent with SU (5) unification, the superpartner masses can vary over a wide range, and may even all lie well beyond the reach of planned colliders. Adding a split 45 to the standard model can also satisfy the unification criteria. so supersymmetric SU (5) is far from unique. Furthermore, we learn that separate Higgs doublets must couple to the top and bottom quarks in order to give a correct m(b)/m(tau) prediction.