Dark matter in universal extra dimension models: Kaluza-Klein photon and right-handed neutrino admixture

We show that in a class of universal extra dimension models (UED), which solves both the neutrino mass and proton decay problem, an admixture of Kaluza-Klein (KK) photon and KK right-handed neutrinos can provide the required amount of cold dark matter (CDM). This model has two parameters R-1 and MZ′ (R is the radius of the extra space dimensions and Z′ the extra neutral gauge boson of the model). Using the value of the relic CDM density, combined with the results from the cryogenic searches for CDM, we obtain upper limits on R-1 of about 400-650 GeV and MZ′≤1.5TeV, both being accessible to the LHC. In some regions of the parameter space, the dark matter-nucleon scattering cross section can be as high as 10-44cm2, which can be probed by the next round of dark matter search experiments.