Dark matter and collider phenomenology in radiative Type-III seesaw model with two inert doublets

We investigate a minimal Type-III scotogenic model featuring two inert scalar doublets and a hyperchargeless triplet fermion. The scalar sector, in addition to the Standard Model Higgs, includes a rich spectrum of dark scalars comprising two CP-even, two CP-odd, and two charged states. This framework gives rise to two viable dark matter candidates: the lightest CP-even dark scalar and the neutral component of the triplet fermion. We perform a comprehensive analysis of both dark matter scenarios, carefully examining their viability under the umbrella of theoretical consistency conditions and experimental constraints. In the inert scalar DM scenario, a significant parameter space emerges below 500 GeV—a region often dubbed the “desert region” in the conventional inert doublet model. Also, in the fermionic DM scenario, a new viable region is identified for DM mass below 2.5 TeV. Furthermore, our extended framework predicts distinctive and novel signatures beyond the conventional collider signatures anticipated for Type-III scotogenic model with one inert doublet.