Higgs Limit and b->s gamma Constraints in Minimal Supersymmetry

Abstract

New limits on the Higgs mass from LEP and new calculations on the radiative (penguin) decay of the b->s gamma branching ratio restrict the parameter space of the Constrained Minimal Supersymmetric Standard Model (CMSSM). We find that for the low tan(beta) scenario only one sign of the Higgs mixing parameter is allowed, while the high tan(beta scenario is practically excluded, if one requires all sparticles to be below 1 TeV and imposes radiative electroweak symmetry breaking as well as gauge and Yukawa coupling unification. For squarks between 1 and 2 TeV high tan(beta) scenarios are allowed. We consider especially a new high tan(beta)=64 scenario with triple unification of all Yukawa couplings of the third generation, which show an infrared fixed point behaviour. The upper limit on the mass of the lightest Higgs in the low (high) tan(beta) scenarios is 97+-6~(120+-2) GeV, where the errors originate predominantly from the uncertainty in the top mass.