PUB - Publikationen an der Universität Bielefeld

We consider the next-to-leading order thermal production rate of heavyright-handed neutrinos in the non-relativistic regime m_top < pi*T << M, wherem_top refers to the electroweak scale. Rephrasing the problem in an OPElanguage and making use of different techniques than a previous analysis bySalvio et al, we confirm the general structure of their result and many of thecoefficients. We also extend the analysis to the next order in thenon-relativistic expansion, thereby revealing the leading non-trivial momentumdependence, as well as to NNLO in couplings, revealing the leading sensitivityto thermal resummations. Our results are expressed as a sum of simple "master"structures, which renders them a suitable starting point for determining thenext-to-leading order rate also in the relativistic regime pi*T ~ M.