title: Temperature dependence of standard model CP violation.
abstract: We analyze the temperature dependence of CP violation effects in the standard model by determining the effective action of its bosonic fields, obtained after integrating out the fermions from the theory and performing a covariant gradient expansion. We find nonvanishing CP violating terms starting at the sixth order of the expansion, albeit only in the C-odd-P-even sector, with coefficients that depend on quark masses, Cabibbo-Kobayashi-Maskawa matrix elements, temperature and the magnitude of the Higgs field. The CP violating effects are observed to decrease rapidly with temperature, which has important implications for the generation of a matter-antimatter asymmetry in the early Universe. Our results suggest that the cold electroweak baryogenesis scenario may be viable within the standard model, provided the electroweak transition temperature is at most of order 1 GeV.
authors.affiliation: Faculty of Physics, University of Bielefeld, D-33615 Bielefeld, Germany and Department of Theoretical Physics, Nuclear Physics Institute ASCR, 25068 Řež, Czech Republic.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Brauner
authors.forename: Olli
authors.initials: O
authors.lastname: Taanila
authors.forename: Anders
authors.initials: A
authors.lastname: Tranberg
authors.forename: Aleksi
authors.initials: A
authors.lastname: Vuorinen