Leptogenesis with triplet Higgs boson

We study the thermal leptogenesis in the scenario where the standard model is extended to include one $SU(2)_{L}$ triplet higgs boson, in addition to three generations of the right-handed neutrinos. Assuming that the lepton number asymmetry is generated by the decays of the lightest right-handed neutrino $N_{1}$, we find that the reheating temperature can be much lowered in this framework, down to the TeV scale, and the left-handed neutrino can have a degenerate spectrum at the order of $m_i \sim 1eV$.