Singlet-doublet dark matter induced radiative neutrino mass and TeV scale leptogenesis

The singlet-doublet dark matter (SDDM) model is a well-motivated WIMP framework that accommodates viable dark matter over a broad range of parameter space. In this work, we explore the possibility of TeV-scale leptogenesis within two realizations of the SDDM setup: Majorana SDDM scenario and Dirac SDDM scenario. The light neutrino mass, in either case, arises radiatively at one loop level. The particles running in the loop are responsible for Dark matter relic and TeV-scale leptogenesis while satisfying other phenomenological constraints. In the Majorana setup, the Standard Model is extended by three generations of singlet fermions $N_i$ and doublet fermions $\Psi_i$, and a singlet scalar $\phi$. The \textit{CP}-violating, out-of-equilibrium decays of the heavier singlets ($N_{2,3}$) generate baryon asymmetry via the leptogenesis route, while the first generation of singlet-doublet fermions give rise to the usual SD Majorana dark matter. In the Dirac setup, the standard model is extended by three generations of complex scalars ($\phi_i$) and right-handed Dirac partners ($\nu_{R_i}$) of SM neutrinos ($\nu_{L_i}$), along with a pair of singlet-doublet fermions $\chi$ and $\Psi$. The \textit{CP}-violating out-of-equilibrium decays of the scalar fields $\phi_i$ generate baryon asymmetry via the Dirac leptogenesis route. We show that in the Majorana setup, successful leptogenesis is possible even in the sub-TeV regime, while in the Dirac setup, the scale of leptogenesis is at a few TeV. With the particle mass at the TeV scale, the model remains promising for collider experiments, particularly through signatures such as prompt decays and displaced vertex searches. In addition, the presence of Dirac neutrinos can contribute to $\Delta N_{\rm eff}$, providing complementary cosmological signatures.