Electroweak Baryogenesis Mechanism Research Articles

Electroweak baryogenesis mediated by locally supersymmetry-breaking defects

We consider the scenario of electroweak baryogenesis mediated by a cosmological defect in models of supersymmetry breaking. When the effective electroweak breaking scale is raised in the defect configuration, the mechanism of electroweak baryogenesis works at a higher energy scale. The baryon charge produced by the mechanism is captured in the defect. It is protected from sphalerons and then released when the defect decays.

Supersymmetric CP-violating currents and electroweak baryogenesis

In this work we compute the CP-violating currents of the right-handed stops and higgsinos, induced by the presence of non-trivial vacuum expectation values of the Higgs fields within the context of the minimal supersymmetric extension of the Standard Model (MSSM) with explicit CP-violating phases. Using the Keldysh formalism, we perform the computation of the currents at finite temperature, in an expansion of derivatives of the Higgs fields. Contrary to previous works, we implement a resummation of the Higgs mass insertion effects to all orders in perturbation theory. While the components of the right-handed stop current jμt̃R become proportional to the difference H2∂μH1−H1∂μH2 (suppressed by Δβ), the higgsino currents, jμH̃i, present contributions proportional to both H2∂μH1±H1∂μH2. For large values of the charged Higgs mass and moderate values of tanβ the contribution to the source proportional to H2∂μH1+H1∂μH2 in the diffusion equations become sizeable, although it is suppressed by the higgsino number violating interaction rate Γμ−1/2. For small values of the wall velocity, 0.04≲vω≲0.1, the total contribution leads to acceptable values of the baryon asymmetry for values of the CP-violating phases ϕCP in the range 0.04≲|sinϕCP|≲1. Finally, we comment on the relevance of the latest results of Higgs searches at LEP2 for the mechanism of electroweak baryogenesis within the MSSM.

Dynamics of two-Higgs-doublet CP violation and baryogenesis at the electroweak phase transition.

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 domain walls, and comparing the exact profile of the CP-violating phase with a commonly used ansatz. We note that the phenomenon of spontaneous CP violation at high temperature can occur in this model, even when there is no 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 tau leptons from the wall gives the dominant effect. We conclude that this mechanism is marginally strong enough to produce the observed baryon asymmetry of the universe.

CP violation and electroweak baryogenesis in extensions of the standard model

We develop a new and general method to calculate the effects of CP violation from extensions of the standard model on the mechanism of electroweak baryogenesis. We illustrate its applicability in the framework of two-higgs doublet models.

Electroweak baryogenesis and standard model CP violation.

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.

Cosmic strings and electroweak baryogenesis

The electroweak symmetry is unbroken in the core of cosmic strings originating from a symmetry breaking at an energy higher than the electroweak scale η EW. The dynamics of such strings may generate a baryon asymmetry below the electroweak symmetry breaking scale. This mechanism for electroweak baryogenesis is most efficient if the scale of string formation is only slightly higher than η EW (e.g. in theories of dynamical symmetry breaking) and if the strings are superconducting. The mechanism is also effective if the electroweak phase transition is second order.

Cosmological lower bound on the EDM of the electron

Multi-Higgs extensions of the standard model provide a natural mechanism for electroweak baryogenesis as well as a substantially big contribution to the dipole electric moments of the elementary particles. In the model with only two Higgs doublets both phenomena originate from one and the same source, namely CP violation in the neutral scalar sector. We present an estimate of the cosmological lower bound on the dipole moment of the electron, which appears to be numerically close to the experimental upper bound.

Electroweak baryogenesis. A numerical study in 1 + 1 dimensions

We study the recently proposed mechanism for electroweak baryogenesis in the standard Weinberg-Salam theory with a non-minimal Higgs sector, through simulations of an analog 1 + 1 dimensional theory, the abelian Higgs model with two Higgs fields. We start from a thermal configuration in the unbroken symmetry phase and mimic the phase transition by changing the scalar potential by hand. We include a term in the effective action obtained by integrating out fermions, which couples a C odd Higgs phase to the Chern-Simons number. The Higgs potential includes a C-violating phase, and this results in a systematic change in the Chern-Simons number of the universe during the transition. The simulations provide the first detailed verification of the electroweak baryogenesis mechanism in an ab initio finite temperature calculation.