Electroweak Baryogenesis and Standard Model CP Violation

TL;DR

This paper critically examines electroweak baryogenesis driven solely by the Standard Model's CKM phase, concluding that QCD damping effects suppress the generated asymmetry to negligible levels, thus challenging the viability of this mechanism.

Contribution

It provides an analytical computation showing that Standard Model CP violation alone cannot produce sufficient baryon asymmetry during the electroweak phase transition.

Findings

QCD damping effects significantly reduce baryon asymmetry

Only a thin bubble layer contributes to quasiparticle scattering

Standard Model CP violation is insufficient for baryogenesis

Abstract

We analyze the mechanism of electroweak baryogenesis proposed by Farrar and Shaposhnikov in which the phase of the CKM mixing matrix is the only source of $CP$ violation. This mechanism is based on a phase separation of baryons via the scattering of quasiparticles by the wall of an expanding bubble produced at the electroweak phase transition. In agreement with the recent work of Gavela, Hern\'andez, Orloff and P\`ene, we conclude that QCD damping effects reduce the asymmetry produced to a negligible amount. We interpret the damping as quantum decoherence. We compute the asymmetry analytically. Our analysis reflects the observation that only a thin, outer layer of the bubble contributes to the coherent scattering of the quasiparticles. The generality of our arguments rules out any mechanism of electroweak baryogenesis that does not make use of a new source of $CP$ violation.