The electroweak phase transition in a nonminimal supersymmetric model

Abstract

We study the electroweak phase transition in a supersymmetric version of the Standard Model, in which a gauge singlet superfield is added to the Higgs sector. We show that the order of the transition is determined by the trilinear soft supersymmetry breaking terms rather than by the O( m 3 T) term in the one-loop, T ≠ 0 corrections. This fact removes the Standard Model upper bound on the Higgs mass, m H < 55 GeV, coming from the requirement that baryon asymmetry is not washed out by anomalous electroweak processes. We perform a numerical analysis of parameter space including in the effective potential the top-stop contribution to one-loop radiative corrections. We find that this model is compatible with the preservation of baryon asymmetry for masses of the lightest scalar up to about 170 GeV.