Leptogenesis in seesaw models with a twofold-degenerate neutrino Dirac mass matrix

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We study leptogenesis in two seesaw models where maximal atmospheric neutrino mixing and Uₑ₃ = 0 result from symmetries. Salient features of those models are the existence of three Higgs doublets and a twofold degeneracy of the neutrino Dirac mass matrix. We find that in those models both leptogenesis and neutrinoless double beta decay depend on the same unique Majorana phase. Leptogenesis can produce a baryon asymmetry of the universe of the right size provided the mass of the heavy neutrino whose decays generate the lepton asymmetry is in the range 10¹¹--10¹² GeV. Moreover, in these models, leptogenesis precludes an inverted neutrino mass spectrum since it requires the mass of the lightest neutrino to be in the range 10⁻³--10⁻² eV.