Testing quasi-Dirac leptogenesis through neutrino oscillations

Abstract

The lightness of the Standard Model (SM) neutrinos could be understood if their masses were to be generated by new physics at a high scale, through the so-called seesaw mechanism involving heavy fermion singlets. We consider a novel scenario where the new physics violates baryon minus lepton number by only a small amount resulting in both heavy fermion singlets and the SM neutrinos to split into pairs of quasi-Dirac states. Above the weak scale, the cosmic matter-antimatter asymmetry can be generated through resonant leptogenesis from decay of heavy singlets. Nontrivially, the CP violation for leptogenesis is bounded from above by the light neutrino mass splitting which can be probed in neutrino oscillation experiments.