Precision corrections to supersymmetric unification

We compute the full set of weak-scale gauge and Yukawa threshold corrections in the minimal supersymmetric standard model, including all finite (non-logarithmic) corrections, which we show to be important. We use our results to examine the effects of unification-scale threshold corrections in the minimal and missing-doublet SU(5) models. We work in the context of a unified mass spectrum, with scalar mass M0 and gaugino mass M12, and find that in minimal SU(5) with squark masses less than one TeV, successful gauge and Yukawa coupling unification requires M12 ⪡ M0 and M0 ⋍ 1 TeV. In contrast, we find that the missing-doublet model permits gauge and Yukawa unification for a wide range of supersymmetric masses.