Dark Matter in Universal Extra Dimension Models: $\gamma_{KK}$ vrs   $\nu_{R,KK}$
  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 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 $M_{Z'}$ ($R$ 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 $M_{Z'}\leq 1.5$ TeV, both being accessible to LHC. In some regions of the parameter space, the dark matter-nucleon scattering cross section can be as high as of $10^{-44}$ cm$^2$, which can be probed by the next round of dark matter search experiments. 
Ken Hsieh, R.N. Mohapatra and Salah Nasri