A new, direct link between the baryon asymmetry and neutrino masses

We point out that, in a class of SO(10) models with matter fields in 16 and 10 representations and type II realization of the seesaw mechanism, the light neutrino masses and the CP asymmetry needed for leptogenesis are controlled by one and the same set of couplings. The generated baryon asymmetry then directly depends on the low-energy neutrino parameters, with no unknown seesaw-scale flavour parameters involved; in particular, the necessary CP violation is provided by the CP-violating phases of the lepton mixing matrix. We compute the CP asymmetry in triplet decays for this scenario and show that it can lead to successful leptogenesis. (C) 2008 Elsevier B.V. All rights reserved.