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Neutrino masses, mixing and leptogenesis in TeV scale B-L extension of the standard model

We address the issue of the neutrino masses and mixing in TeV scale $B-L$ extension of the Standard Model. We show that if Dirac neutrino masses are of order $10^{-4}$ Gev, then the measured neutrino masses are correctly obtained. We propose a mass relation between quarks and leptons that may account for such small Dirac neutrino masses. We analyze the leptogenesis in this type of models and provide analytical expressions for the new contributions due to the predicted extra Higgs and extra neutral gauge boson. We find that thermal leptogenesis, with a resonant enhancement due to nearly degenerate right-handed neutrinos, can yield sufficient baryon asymmetry. Finally, we comment on a possible scheme for non-thermal leptogenesis, which is due to the decay of extra Higgs into right-handed neutrino.