Abstract
The origin of the matter-antimatter asymmetry of the universe remains unexplained in the Standard Model (SM) of particle physics. The origin of the flavour structure is another major puzzle of the theory. In this article, we report on recent work attempting to link the two themes through the appealing framework of electroweak (EW) baryogenesis. We show that Yukawa couplings of SM fermions can be the source of CP violation for EW baryogenesis if they vary at the same time as the Higgs is acquiring its vacuum expectation value, offering new avenues for EW baryogenesis. The advantage of this approach is that it circumvents the usual severe bounds from electric dipole moments. These ideas apply if the mechanism explaining the flavour structure of the SM is connected to EW symmetry breaking, as motivated for instance in Randall-Sundrum or Composite Higgs models. We compute the resulting baryon asymmetry for different configurations of the Yukawa coupling variation across the bubble wall and show that it can naturally be of the right order.This article is part of the Theo Murphy meeting issue 'Higgs cosmology'.
Highlights
All fermion masses in the Standard Model (SM), apart form the top quark, are much smaller than the electroweak (EW) scale
We report on recent work connecting flavour cosmology and baryogenesis [1,2,3,4]
For a source located in the symmetric phase, where both particles have a nearly vanishing mass, the cancellation is very much unsuppressed. This analysis shows that for the parametrization (3.4) and assuming the same n for all flavours, models with a source located inside the broken phase are generally more effective in producing the baryon asymmetry even though we naively expect the mechanism to be more effective when the source is located in front of the bubble wall
Summary
All fermion masses in the Standard Model (SM), apart form the top quark, are much smaller than the electroweak (EW) scale. Electroweak baryogenesis (EWBG) is a mechanism to explain the matter–antimatter asymmetry of the universe using SM baryon number violation [5] It relies on a charge transport mechanism in the vicinity of bubble walls during a first-order EW phase transition [6]. New sources that have been commonly studied in the literature are either in the chargino/neutralino mass matrix [8,9,10,11,12,13] or the sfermion sector in supersymmetric models [8,9,14,15] or coming from a varying top quark Yukawa coupling [16,17] as motivated in composite Higgs models [18] or in two-. Very different from that in [28,29], which is very constrained experimentally
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