We explore a minimal extension of the standard model with fermionic cold dark matter by introducing a gauge singlet Dirac fermion. The interactions between the dark matter and the standard model matters are described by the nonrenormalizable dimension-5 term. We show that the measured relic abundance of the cold dark matter can be explained in our model and predict the direct detection cross section. The direct search of the dark matter provides severe constraints on the mass and coupling of the minimal fermionic dark matter with respect to the Higgs boson mass.

• Received 1 November 2006

DOI:https://doi.org/10.1103/PhysRevD.75.115012