We explore the phenomenology of Kaluza-Klein (KK) dark matter in
very general models with universal extra dimensions (UEDs), emphasizing the
complementarity between high-energy colliders and dark matter direct detection
In models with relatively small mass splittings between the dark matter
candidate and the rest of the (colored) spectrum, the collider
sensitivity is diminished, but direct detection rates are enhanced.
UEDs provide a natural framework for such mass degeneracies.
We consider both 5-dimensional and 6-dimensional non-minimal UED models,
and discuss the detection prospects for various KK dark matter candidates:
the KK photon, the KK Z-boson, the KK Higgs boson (all 5D) and the spinless KK
We combine collider limits such as electroweak precision data and expected
LHC reach, with cosmological constraints from WMAP, and the
sensitivity of current or planned direct detection experiments.
Allowing for general mass splittings,
we show that neither colliders, nor direct detection
experiments by themselves can explore all of the relevant
KK dark matter parameter space. Nevertheless, they probe different
parameter space regions, and the combination of the two types of
constraints can be quite powerful. For example, in the case of the
KK photon in 5D UEDs the relevant parameter space will be almost completely
covered by the combined LHC and direct detection sensitivities expected in the