Dark Matter in Inert Triplet Models

We study the inert triplet models, in which the standard model (SM) is extended to have a new SU(2)L triplet scalar (Y=0 or 2) with an Z2 symmetry. We show that the neutral component of the triplet can be a good dark matter candidate. In particular, for the hypercharge Y=0 triplet model, the WMAP data favors the region where the dark matter mass is around 5.5 TeV, which is also consistent with the direct detection experiments. In contrast, for the Y=2 model, although dark matter with its mass around 2.8 TeV is allowed by WMAP, it is excluded by the direct detection experiments because the spin-independent cross section is enhanced by the Z mediated tree-level scattering process.