Soft Masses in Strong Unification

We examine the infra-red structure of soft supersymmetry breaking masses of the squarks and sleptons in supersymmetric (SUSY) strong unification schemes where αGUT ∼ 0.2− 1. We show that combinations of soft masses approach fixed points which leads to very simple predictions for soft masses at the intermediate scale. The assumption that the high energy gaugino mass M1/2 dominates over the soft scalar masses leads to a strong suppression of flavour changing neutral currents, and a low energy SUSY spectrum which is simply predicted in terms of two parameters, namely αGUT and M1/2. Due to the quickly falling gauge couplings beneath the high energy scale, the low energy spectrum has a characteristic “scalar dominated” signature quite unlike the standard gaugino dominated MSSM where the right-handed sleptons are predicted to be rather light. We also examine the new sources of flavour changing expected in such models, and in particular show that the flavour violation coming from the D-term of a U(1)X gauged family symmetry may be reduced to an acceptable level. CERN-TH/98-27 February 1, 2008 On leave of absence from Department of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, U.K.