RENORMALIZATION-GROUP STUDY OF THE STANDARD MODEL AND ITS EXTENSIONS - THE MINIMAL SUPERSYMMETRIC STANDARD MODEL

In this paper we summarize the minimal supersymmetric standard model a s well as the renormalization group equations of its parameters. We pr oceed to examine the feasibility of the model when the breaking of sup ersymmetry is parametrized by the soft terms suggested by supergravity theories. In such models, the electroweak symmetry is exact at the tr ee level and is broken spontaneously at one-loop order. We make the ad ditional assumption that the GUT-inspired relation M(b) = m(tau) be va lid at the scale where the gauge coupling constants unify, which const rains the value of the top quark mass. For all types of soft breaking terms expected in supergravity theories, we present the results of num erical runs which yield electroweak breaking at the required scale. Th ese yield not only the allowed ranges for the soft supersymmetry break ing parameters, but also the value of the supersymmetric partners' mas ses. Taking M(b) = m(tau) at the unification scale, M(b) = 4.9 GeV, an d alpha3(M(Z)) = 0.118, we find that for models in which global supers ymmetry breaking arises solely from soft gaugino masses and bilinear m ixing between the two Higgs scalars the top quark mass can be no light er than approximately 180 GeV.