PRECISION ELECTROWEAK DATA, SUPERSYMMETRY AND GUTS

Following an update of indirect constraints on m(t), M(H) and alpha(s)(M(Z))\MSBAR; from precision electroweak measurements in the Standard Model, we analyze the data within the context of the Minimal Supersymmetric extension of the Standard Model (MSSM), including the constraint from supersymmetric grand unification. Within the Standard Model, we find somewhat larger values of m(t) and M(H) than previously, and a somewhat lower value of alpha(s)(M(Z))\MSBAR. The favoured value of m(t) can be decreased (increased) by O(10 to 20) GeV if the scalar particle masses (lightest chargino mass) are close to the direct experimental limits. We find for the first time a significant lower limit on supersymmetric Higgs masses. The supersymmetric GUT constraint gives a coupled upper limit on the scalar and gaugino masses that depends sensitively on the other MSSM parameters.