Electroweak Baryogenesis in a Two-Higgs Doublet Model

Electroweak baryogenesis fails in the SM because of too small CP violation and the lack of a strong first-order phase transition. It has been shown that supersymmetric models allow for successful baryogenesis, where the Higgsinos play an important role in the transport processes that generate the asymmetry. I will demonstrate that also non-supersymmetric models can provide the observed baryon asymmetry. The top quark takes the role of the Higgsinos. Focusing on the two-Higgs doublet model, I will discuss details of the phase transition and consequences for Higgs physics and EDM searches.Comment: 5 pages, 2 figures. Proceedings of Moriond 2006, Electroweak Session. 11-18 March, La Thuile (Italy

The bubble wall velocity in the minimal supersymmetric light stop scenario

We build on existing calculations of the wall velocity of the expanding bubbles of the broken symmetry phase in a first-order electroweak phase transition within the light stop scenario (LSS) of the MSSM. We carry out the analysis using the 2-loop thermal potential for values of the Higgs mass consistent with present experimental bounds. Our approach relies on describing the interaction between the bubble and the hot plasma by a single friction parameter, which we fix by matching to an existing 1-loop computation and extrapolate it to our regime of interest. For a sufficiently strong phase transition (in which washout of the newly-created baryon asymmetry is prevented) we obtain values of the wall velocity, v_w~0.05, far below the speed of sound in the medium, and not very much deviating from the previous 1-loop calculation. We also find that the phase transition is about 10% stronger than suggested by simply evaluating the thermal potential at the critical temperature.Comment: 17pages, 3 figure

Baryogenesis at the Electroweak Phase Transition for a SUSY Model with a Gauge Singlet

SUSY models with a gauge singlet easily allow for a strongly first order electroweak phase transition (EWPT). We discuss the wall profile, in particular transitional CP violation during the EWPT. We calculate CP violating source terms for the charginos in the WKB approximation and solve the relevant transport equations to obtain the generated baryon asymmetry.Comment: 5 pages, 6 figures. To appear in the Proceedings of Strong and Electroweak Matter 2000 (SEWM2000), Marseilles; a reference adde

Electric dipole moment constraints on minimal electroweak baryogenesis

We study the simplest generic extension of the Standard Model which allows for conventional electroweak baryogenesis, through the addition of dimension six operators in the Higgs sector. At least one such operator is required to be CP-odd, and we study the constraints on such a minimal setup, and related scenarios with minimal flavor violation, from the null results of searches for electric dipole moments (EDMs), utilizing the full set of two-loop contributions to the EDMs. The results indicate that the current bounds are stringent, particularly that of the recently updated neutron EDM, but fall short of ruling out these scenarios. The next generation of EDM experiments should be sufficiently sensitive to provide a conclusive test.Comment: 20 pages, 5 figures; v2: comments added and minor corrections to the results, published versio

Suppressing lepton flavor violation in a soft-wall extra dimension

A soft-wall warped extra dimension allows one to relax the tight constraints imposed by electroweak data in conventional Randall-Sundrum models. We investigate a setup, where the lepton flavor structure of the standard model is realized by split fermion locations. Bulk fermions with general locations are not analytically tractable in a soft-wall background, so we follow a numerical approach to perform the Kaluza-Klein reduction. Lepton flavor violation is induced by the exchange of Kaluza-Klein gauge bosons. We find that rates for processes such as muon-electron conversion are significantly reduced compared to hard-wall models, allowing for a Kaluza-Klein scale as low as 2 TeV. Accommodating small neutrino masses forces one to introduce a large hierarchy of scales into the model, making pressing the question of a suitable stabilization mechanism

Cosmological signatures of a UV-conformal standard model

Quantum scale invariance in the UV has been recently advocated as an attractive way of solving the gauge hierarchy problem arising in the Standard Model. We explore the cosmological signatures at the electroweak scale when the breaking of scale invariance originates from a hidden sector and is mediated to the Standard Model by gauge interactions (Gauge Mediation). These scenarios, while being hard to distinguish from the Standard Model at LHC, can give rise to a strong electroweak phase transition leading to the generation of a large stochastic gravitational wave background in possible reach of future space-based detectors such as eLISA and BBO. This relic would be the cosmological imprint of the breaking of scale invariance in Nature

Top transport in electroweak baryogenesis

In non-supersymmetric models of electroweak baryogenesis the top quark plays a crucial role. Its CP-violating source term can be calculated in the WKB approximation. We point out how to resolve certain discrepancies between computations starting from the Dirac equation and the Schwinger--Keldysh formalism. We also improve on the transport equations, keeping the W-scatterings at finite rate. We apply these results to a model with one Higgs doublet, augmented by dimension-6 operators, where our refinements lead to an increase in the baryon asymmetry by a factor of up to about 5.Comment: 17 pages, 3 figures, references adde

Seesaw Mechanism in Warped Geometry

We show how the seesaw mechanism for neutrino masses can be realized within a five dimensional (5D) warped geometry framework. Intermediate scale standard model (SM) singlet neutrino masses, needed to explain the atmospheric and solar neutrino oscillations, are shown to be proportional to M_Pl\exp((2c-1)\pi kR), where c denotes the coefficient of the 5D Dirac mass term for the singlet neutrino which also has a Planck scale Majorana mass localized on the Planck-brane, and kR~11 in order to resolve the gauge hierarchy problem. The case with a bulk 5D Majorana mass term for the singlet neutrino is briefly discussed.Comment: 14 pages, LaTeX, 4 figures, references adde