PUB - Publikationen an der Universität Bielefeld

The rates for lepton number washout in extensions of the Standard Modelcontaining right-handed neutrinos are key ingredients in scenarios forbaryogenesis through leptogenesis. We relate these rates to real-timecorrelation functions at finite temperature, without making use of any particleapproximations. The relations are valid to quadratic order in neutrino Yukawacouplings and to all orders in Standard Model couplings. They take into accountall spectator processes, and apply both in the symmetric and in the Higgs phaseof the electroweak theory. We use the relations to compute washout rates atnext-to-leading order in g, where g denotes a Standard Model gauge or Yukawacoupling, both in the non-relativistic and in the relativistic regime. Even inthe non-relativistic regime the parametrically dominant radiative correctionsare only suppressed by a single power of g. In the non-relativistic regimeradiative corrections increase the washout rate by a few percent at hightemperatures, but they are of order unity around the weak scale and in therelativistic regime.