Efficient electroweak baryogenesis from lepton transport

Several mechanisms through which a baryon asymmetry would be generated at the electroweak phase transition have been suggested, most employing $CP$ violation in the Higgs sector of minimal extensions of the standard model. One mechanism involves propagation of particle asymmetries generated by the bubble walls into the unbroken phase where it drives baryon number violation. Hitherto attention has focussed on top quarks because of their large Yukawa couplings and thus effective scattering from bubble walls. In this paper we point out that leptons can be more efficient mediators of electroweak baryogenesis, especially so in the case of thick bubble walls, predicted by perturbative calculations. We carry out an analytic calculation of each stage of the mechanism and conclude it produces a baryon asymmetry compatible with observations for a wide range of parameters.