1 Niels Bohr International Academy, The Niels Bohr Institute, Faculty of Science, Københavns Universitet2 Theoretical Particle Physics and Cosmology, The Niels Bohr Institute, Faculty of Science, Københavns Universitet3 University of Bielefeld4 Niels Bohr International Academy, The Niels Bohr Institute, Faculty of Science, Københavns Universitet
CP violation in the standard model originates from the Cabibbo-Kobayashi-Maskawa mixing matrix. Upon integrating all fermions out of the theory, its effects are captured by a series of effective nonrenormalizable operators for the bosonic gauge and Higgs fields. We compute the CP-violating part of the effective action to the leading nontrivial, sixth order in the covariant gradient expansion as a function of temperature. In the limit of zero temperature, our result addresses the discrepancy between two independent calculations existing in the literature [1, 2]. We find that CP violation in the standard model is strongly suppressed at high temperature, but that at T less than or similar to 1 GeV it may be relevant for certain scenarios of baryogenesis. We also identify a selected class of operators at the next, eighth order and discuss the convergence of the covariant gradient expansion.
Journal of High Energy Physics (online), 2012, Vol 76, Issue 11, p. 1-32
CP violation; Thermal Field Theory; Standard Model