Sources for Electroweak Baryogenesis

Abstract

I review a computation of the baryon asymmetry arising from a first order electroweak phase transition in the Minimal Supersymmetric Standard model by classical force mechanism (CFM). I focus on CP violation provided by the charginos and show that it is the usually neglected sum of the two Higgsino fields, H_1+H_2, which gives a larger contribution to the baryon asymmetry than does the combination H_1-H_2. In fact, the latter contribution is exactly zero in CFM, because it is associated with a phase transformation of the fields. Baryogenesis is found to be most effective in MSSM CFM when only $\tilde t_R$ is light, which lends independent support for the "light stop scenario", and it remains viable for CP-violating phases as small as δ_μ\sim {\it few} \times 10^{-3}.