Leptogenesis in a Prompt Decay Scenario

Leptogenesis is studied within the seesaw neutrino mass model in a regime where all sterile neutrinos have prompt rather than delayed decays. It is shown that during neutrino thermal production lepton asymmetries are generated in both active lepton and sterile neutrino sectors. The large B −L asymmetry is slowly pumped into the chemically decoupled right-handed quarks and leptons and baryon number sector which later protect B −L from fast L violating processes. The dependence of the final baryon asymmetry on couplings and masses is totally different from the decay scenario. B does not vanish in the limit of degenerate light neutrinos and the observed asymmetry is naturally obtained for a sum of square masses, m̄, between the atmospheric neutrino mass gap and 0.2 eV.