The Electroweak Phase Transition in the Minimal Supersymmetric Standard Model

TL;DR

This paper develops a 3D effective theory for the MSSM at finite temperature to analyze the electroweak phase transition, finding that supersymmetric scalars strengthen the transition and that a very light stop is not essential for baryogenesis.

Contribution

It introduces a systematic dimensional reduction approach for the MSSM and related models, providing new insights into the conditions for electroweak baryogenesis.

Findings

Including all supersymmetric scalars enhances the phase transition strength.

A very light stop is not required for successful baryogenesis.

The phase transition can be sufficiently first order if the lightest Higgs mass is below 70 GeV.

Abstract

Using dimensional reduction we construct an effective 3D theory of the Minimal Supersymmetric Standard Model at finite temperature. The final effective theory is obtained after three successive stages of integration out of massive particles. We obtain the full 1-loop relation between the couplings of the reduced theory and the underlying 4D couplings and masses. The procedure is also applied to a general two Higgs doublet model and the Next to Minimal Supersymmetric Standard Model. We analyze the effective 3D theory constructed for the MSSM to determine the regions of parameter space for which electroweak baryogenesis is possible. We find that the inclusion of all supersymmetric scalars has the effect of enhancing the strength of the phase transition. The requirement of a very light stop is not necessary for baryogenesis. The phase transition is sufficiently first order if the lightest Higgs mass, $m_{h} ~< 70$ GeV. We note the existence of potentially interesting regions of parameter space for which existing analysis techniques are inadequate to decide the question.