[Araki, Takeshi] Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
; [Geng, C. Q.
; Nagao, Keiko I.] Natl Tsing Hua Univ, Dept Phys, Hsinchu 300, Taiwan
; [Geng, C. Q.] Natl Ctr Theoret Sci, Hsinchu 300, Taiwan
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 Z(2) 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.