PRECISION CORRECTIONS TO SUPERSYMMETRIC UNIFICATION

We compute the full set of weak-scale gauge and Yukawa threshold corre ctions in the minimal supersymmetric standard model, including ah fini te (non-logarithmic) corrections, which we show to be important. We us e our results to examine the effects of unification-scale threshold co rrections in the minimal and missing-doubler SU(5) models. We work in the context of a unified mass spectrum, with scalar mass M(0) and gaug ino mass M(1/2), and find that in minimal SU(5) with squark masses les s than one TeV, successful gauge and Yukawa coupling unification requi res M(1/2) << M(0) and M(0) similar or equal to 1 TeV. In contrast, we find that the missing-doubler model permits gauge and Yukawa unificat ion for a wide range of supersymmetric masses.