Leptogenesis constraints on the mass of right-handed gauge bosons

We discuss leptogenesis constraints on the mass of the right- handed W boson ( WR) in a TeV- scale leftright seesaw model for neutrino masses. For generic Dirac mass of the neutrinos, i. e. with all Yukawa couplings. 10- 5.5, it has been pointed out that successful leptogenesis requires a lower bound of 18 TeVon the WR mass, pushing it beyond the reach of the LHC. Such TeV- scale left- right seesaw model must, however, be parity asymmetric for type- I seesaw to give the observed neutrino masses. This class of models can accommodate larger Yukawa couplings, which give simultaneous fits to charged- lepton and neutrino masses, by invoking either cancellations or specific symmetry textures for Dirac ( MD) and Majorana ( MN) masses in the seesaw formula. We show that in this case the leptogenesis bound on MWR can be substantially weaker, i. e. MWR. 3 TeV for MN. MWR. This happens due to considerable reduction of the dilution effects from WR- mediated decays and scatterings, while the washout effects due to inverse decays are under control for certain parameter ranges of the Yukawa couplings. We also show that this model is consistent with all other low- energy constraints, such as lepton flavor violation and neutrinoless double beta decay. Thus, a discovery of the right- handed gauge bosons alone at the LHC will not falsify leptogenesis as the mechanism behind the matter- antimatter asymmetry in our Universe.