The electroweak phase transition in minimal supergravity models

Abstract

We explore the electroweak phase transition in minimal supergravity models by extending our previous analysis of the one-loop Higgs potential to include finite temperature effects. Minimal supergravity is characterized by two Higgs doublets at the electroweak scale, gauge coupling unification, and universal soft-SUSY breaking at the unification scale. We have searched for the allowed parameter space where the phase transition is sufficiently first order to avoid washout of baryon number after the phase transition via unsuppressed anomalous electroweak sphaleron processes. This requirement imposes strong constraints on the Higgs sector; we find m h ≲ 60 GeV (at one loop) and tan ß ≲ 2. We argue that present Higgs searches rule out this remaining parameter space. Thus, if supergravity (with two light Higgs doublets) is to allow for baryogenesis, it must also provide for B− L production at or above the weak scale. Our results therefore indicate that the field/coupling content of minimal supergravity is insufficient to account for the baryon asymmetry of the universe (BAU). We suggest that the no-scale flipped SU (5) supergravity model naturally and economically provides a source of B− L violation and can account for the observed ratio n B n γ ∼10 −10 .