Bubble wall velocity in the minimal supersymmetric light stop scenario

We build on existing calculations of the wall velocity of the expanding bubbles of the broken symmetry phase in a first-order electroweak phase transition within the light stop scenario (LSS) of the MSSM. We carry out the analysis using the 2-loop thermal potential for values of the Higgs mass consistent with present experimental bounds. Our approach relies on describing the interaction between the bubble and the hot plasma by a single friction parameter, which we fix by matching to an existing 1-loop computation and extrapolate to our regime of interest. For a sufficiently strong phase transition (in which washout of the newly created baryon asymmetry is prevented) we obtain values of the wall velocity, v_w≈0.05, far below the speed of sound in the medium, and not very much deviating from the previous 1-loop calculation. We find that the phase transition is about 10% stronger than suggested by simply evaluating the thermal potential at the critical temperature. We also comment on the relevance of our results to extended models, such as the NMSSM.