Nonlocal electroweak baryogenesis. I. Thin wall regime

We investigate ``nonlocal'' schemes for baryogenesis at a first-order electroweak phase transition, in which the effects of a CP-violating condensate on the bubble wall propagate into the unbroken phase where the sphaleron rate is unsuppressed. Such a condensate exists in multi-Higgs-boson extensions of the standard model, and may exist due to an instability in the minimal standard model. In this paper we first discuss the general problem of determining the perturbations induced by a CP-violating condensate, distinguishing two regimes (quantum and classical). We then give an analytic treatment of quantum-mechanical reflection in the thin wall regime, in which interactions with the plasma can be neglected as a particle propagates across the wall. We focus on leptons because of their much weaker coupling to the plasma. We argue that they are likely to be accurately described by this calculation, but quarks are not. The relative magnitude of the baryon asymmetry produced for different fermions depends on their relative Yukawa couplings (not their zero temperature masses), their transport properties, and their interactions. We calculate the baryon asymmetry for various parameter ranges and conclude that asymmetries comparable with observations can be generated. 1996 The American Physical Society.