Thermal leptogenesis in the Babu-Nandi-Tavartkiladze model of neutrino mass

This is the authors' abstract. We don't add key points for this paper.

We investigate neutrino mass and thermal leptogenesis in the Babu-Nandi-Tavartkiladze model featuring a scalar quadruplet ( Φ ) and a pair of vectorlike fermion triplets ( Σ ). In this framework, neutrino masses are generated via an effective dimension-7 operator L L H H ( H † H ) / Λ 3 at the tree level and via the dimension-5 operator L L H H / Λ at the one-loop level. It naturally accommodates sub-eV neutrino masses even if the new physics scale Λ is O ( TeV ) , thus making the model a compelling target for experimental searches. We explore the viability of thermal leptogenesis in this model, which is distinct from the canonical seesaw-based leptogenesis due to the presence of vector-like fermions. We find that leptogenesis is viable for M Σ ≳ 10 7 GeV for a hierarchical spectrum of fermion triplets. However, in the quasidegenerate regime, resonant enhancement of the CP asymmetry lowers this scale down to O ( TeV ) , reconciling successful leptogenesis with the originally motivated TeV-scale phenomenology and testability of the model at colliders.