Neutrino mass, scalar dark matter, and collider signatures in a radiative doublet-triplet model

Abstract

We explore a radiative neutrino mass model based on the topology T4-3-i, which is a one-loop completion of the Weinberg operator. We focus on its T4-3-i-C1 realization, containing an inert scalar doublet, a real scalar triplet, a Majorana fermion triplet, and a Dirac singlet fermion. An exact $Z_2$ symmetry forbids the tree-level type-III term and stabilizes the lightest $Z_2$-odd particle, leaving the one-loop topology as the leading source of neutrino mass. The model accomodate a neutral {\it CP}-even scalar dark matter candidate and predicts a rank two neutrino mass matrix, and thus one neutrino is massless. A combined analysis incorporating theoretical and experimental constraints reveals viable solutions to both neutrino mass orderings, with the inverted ordering predicting larger values of $m_{\beta\beta}$, $m_\beta$, and $\sum_i m_i$, thereby enhancing its testability through future beta-decay, neutrinoless double beta decay, and cosmological probes. Within the same viable parameter region, the observed dark matter relic abundance is accounted for by annihilation and coannihilation processes, while the electroweak triplet sector gives rise to prompt, displaced, or long-lived particle signatures, offering complementary collider probes to dark matter and low-energy searches.