Electroweak baryogenesis and standard modelCPviolation

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, Hernández, Orloff and Pène, 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.

Chern-Simons and winding number in a tachyonic electroweak transition

“…Of course, one is also interested in the CP violation from the CKM matrix. As mentioned above, this CP violation has been estimated to be much too small for baryogenesis [6,7,8], but these estimates do not seem to apply to a tachyonic transition at zero temperature. In fact, it has been suggested [20] that the effect might be much larger in this case.…”

“…It is widely believed that a crossover transition is too close to equilibrium for creation of the asymmetry. Furthermore, the CKM CP violation has been found to be much too small [6,7,8].…”

Fermionic dispersion relations in the standard model at finite temperature

“…Thus, the imaginary part of the QCD self-energy is much larger than the electroweak contributions to the real part of the self-energy for all quarks but the top. This means that coherent electroweak quantum phenomena associated to quarks (for instance, CP violation) cannot take place in the plasma because the lifetime of the quasi-particles is very small with respect to the characteristic time of the electroweak processes [2,12]. When a quasi-particle scatters, the electroweak coherence is lost.…”

“…The quantum spatial coherence, i.e. the phase relation between points separated by a distance ≥ | v|/2γ, is lost [2,12]. Since we are interested in obtaining the branches which describe the quasi-particles, only the real part of the one-loop contribution to the self-energy will be calculated.…”

MSSM electroweak baryogenesis and LHC data

“…However for Higgs masses in the allowed range the electroweak phase transition in the SM is a cross-over, and therefore the mechanism of Electroweak Baryogenesis (EWBG) is not realized [7][8][9][10]. Moreover even if the phase transition were strong enough, the SM CP-violating sources are too weak to lead to the observed baryon asymmetry [11][12][13][14].…”