Leptogenesis in U(1) Extensions of the Standard Model

We present the ingredients of a computation needed for a semi-classical treatment for estimating the amount of baryogenesis via leptogenesis. Our main focus is on the computation of the finite temperature CP-asymmetry factor originating from Majorana fermion decays into a lepton and a scalar particle at next-to-leading order in perturbation theory. Such decays emerge naturally in U(1) extensions of the Standard Model, such as the superweak extension (SWSM). We emphasize the importance of all cuts in the one-loop corrections in order to obtain physically meaningful expressions and present benchmark predictions for the CP-asymmetry factor as a function of temperature in the SWSM. Abstract Published by the Jagiellonian University 2026 authors