Dynamics of two-Higgs-doublet<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>CP</mml:mi></mml:math>violation and baryogenesis at the electroweak phase transition

Abstract

We quantitatively study the charge transport mechanism of electroweak baryogenesis in a realistic two-Higgs-doublet model, comparing the contributions from quarks and leptons reflecting from electroweak do-main walls, and comparing the exact profile of the $\mathrm{CP}$-violating phase with a commonly used ansatz. We note that the phenomenon of spontaneous $\mathrm{CP}$ violation at high temperature can occur in this model, even when there is no $\mathrm{CP}$ violation at zero temperature. We include all known effects which are likely to influence the baryon production rate, including strong sphalerons, the nontrivial dispersion relations of the quasiparticles in the plasma, and Debye screening of gauged charges. We confirm the claim of Joyce, Prokopec, and Turok that the reflection of $\ensuremath{\tau}$ leptons from the wall gives the dominant effect. We conclude that this mechanism is at best marginally capable of producing the observed baryon asymmetry of the universe, and we discuss some ways in which it might be enhanced.