PUB - Publikationen an der Universität Bielefeld

CP violation in the standard model originates from theCabibbo-Kobayashi-Maskawa mixing matrix. Upon integrating all fermions out ofthe theory, its effects are captured by a series of effective nonrenormalizableoperators for the bosonic gauge and Higgs fields. We compute the CP-violatingpart of the effective action to the leading nontrivial, sixth order in thecovariant gradient expansion as a function of temperature. In the limit of zerotemperature, our result addresses the discrepancy between two independentcalculations existing in the literature [1,2]. We find that CP violation in thestandard model is strongly suppressed at high temperature, but that at T<1GeVit may be relevant for certain scenarios of baryogenesis. We also identify aselected class of operators at the next, eighth order and discuss theconvergence of the covariant gradient expansion.