Dark matter in inert triplet models

We study the inert triplet models, in which the standard model 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.