MINIMAL SUPERSYMMETRIC UNIFICATION PREDICTIONS

We re-examine the predictions for the gauge couplings in the minimal extension of the standard model which result from the assumption that the model comes from a unified theory with a single scale of breaking. The effects of thresholds are considered both at the unification scale and at the low-energy scale of the new supersymmetric states. The latter are found to be particularly important and are analysed using the supergravity spectrum corresponding to common scalar and gaugino masses plus other soft supersymmetry breaking terms corrected by gauge and Yukawa radiative corrections. The analysis is extended to include the prediction for the W-boson mass coming from the radiatively induced spontaneous symmetry breaking of the standard model. The requirement that this be within the measured value without fine tuning strongly limits the magnitude of the supersymmetry breaking scale and the resulting predictions for the detailed mass spectrum of the supersymmetric states and the Higgs bosons. The bottom quark mass is also determined using the full two-loop renormalisation group equation with the unification prediction m(b) = m(tau) at the compactification scale.