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Dark matter and scalar sector in a novel two-loop scotogenic neutrino mass model

We propose an extended $3+1$ Higgs doublet model where the Standard Model (SM) gauge structure is enhanced by the discrete symmetry $Q_6 \times Z_2 \times Z_4$, and the fermion content is extended with right-handed Majorana neutrinos. The scalar sector, besides four $SU(2)$ doublets, incorporates multiple gauge-singlet scalars. In our model, the tiny active neutrino masses arise from a novel radiative seesaw mechanism at two-loop level and the leptonic mixing features the cobimaximal mixing pattern compatible with neutrino oscillation experimental data. Along with this, the proposed model is consistent with SM quark masses and mixings as well as with the constraints arising from dark matter relic density and dark matter direct detection. Our analysis reveals that the best-fit point satisfying dark matter constraints yields a non-SM scalar with mass near $95$ GeV, which could be a possible candidate for the observed $95$ GeV diphoton excess. We further obtain other non SM scalars with masses at the subTeV scale which are within the LHC reach, while successfully complying with the experimental bounds arising from collider searches.