Sommerfeld Enhancement in Radiative neutrino Mass Models with Large Scalar Multiplets

We investigate the Sommerfeld enhanced Dark Matter (DM) annihilation cross sections into $WW$, $ZZ$, $\gamma\gamma$ and $\gamma Z$ at present day in the galactic halo for DM candidates in models of Radiative Neutrino Mass generation with large electroweak multiplets. Firstly, we focus on scalar DM of one-loop radiative neutrino mass model (Scotogenic Model) and study the annihilation cross-sections for scalar doublet and its immediate generalization, the quartet in their respective viable region of parameter space. Secondly, we consider fermionic DM of three-loop radiative neutrino mass model (Krauss-Nasri-Trodden Model) and study the annihilation cross-sections for 5-plet and 7-plets respectively. In both cases, we find that larger multiplets have sizable Sommerfeld enhanced cross-sections compared to the smaller multiplets and are more constrained by the current H.E.S.S. observation and future CTA sensitivity limits.