SUSY AND THE ELECTROWEAK PHASE-TRANSITION

We analyze the effective three-dimensional theory previously construct ed for the MSSM and multi-Higgs models to determine the regions of par ameter space in which the electroweak phase transition is sufficiently strong for a B + L asymmetry to survive in the low-temperature phase. We find that the inclusion of all supersymmetric scalars and all one- loop corrections has the effect of enhancing the strength of the phase transition. Without a light stop or extension of the MSSM the phase t ransition is sufficiently first order only if the lightest Higgs mass M-h less than or similar to 70 GeV and tan beta less than or similar t o 1.75. (C) 1997 Published by Elsevier Science B.V.