Dark matter in the Georgi-Machacek model with an additional inert doublet

Abstract: We study a model that extends the Georgi-Machacek model by the addition of an inert doublet, $\Phi_2$. This allows for the model to contain a natural dark matter candidate, $H^0$. For a number of benchmark points at two DM candidate masses ($m_{H^0} \in {70,\,250}$ GeV), we determine the relic abundance, direct detection cross section, and collider constraints. We find that the collider studies used do not constrain the model. For the parameter region chosen, the points are ruled out by direct detection experimental results. At the lower mass point, we do not find a viable parameter point, while at the higher mass we do find an additional point that satisfies all the applied constraints.