Leptogenesis in the minimal flipped SU(5) unification

Abstract

We study the prospects of thermal leptogenesis in the framework of the minimal flipped SU(5) unified model in which the right-handed (RH) neutrino mass scale emerges as a two-loop effect. Despite its strong suppression with respect to the unification scale that tends to disfavor leptogenesis in the standard Davidson-Ibarra regime (and a notoriously large washout of the N1-generated asymmetry owing to a toplike Yukawa entry in the Dirac neutrino mass matrix) the desired ηB∼6×10−10 can still be attained in several parts of the parameter space exhibiting interesting baryon and lepton number violation phenomenology. Remarkably enough, in all these regions the mass of the lightest left-handed (LH) neutrino is so low that it yields mβ≲0.03  eV for the effective neutrino mass measured in beta decay, i.e., an order of magnitude below the design sensitivity limit of the KATRIN experiment. This makes the model potentially testable in the near future. Published by the American Physical Society 2024