ELECTROWEAK PHASE-TRANSITION IN SUPERSYMMETRY

The electroweak phase transition in supersymmetric models is studied, analyzing the constraint on the Higgs-boson mass coming from the condition that the cosmic baryon asymmetry is not washed out soon after the phase transition. It is found that, in the minimal supersymmetric model, baryogenesis at the weak scale requires a Higgs boson lighter than about 50-55 GeV, as in the standard model. This result holds true also when the one-loop radiative corrections, which are important for a heavy top quark, are taken into account. On the other hand, in extended supersymmetric models, it is possible to have the lightest Higgs boson as heavy as 100 GeV and still satisfy the requirement of weak-scale baryogenesis.