A dark matter candidate from an extra (non-universal) dimension

We show that a recently constructed five-dimensional (5D) model withgauge-Higgs unification and explicit Lorentz symmetry breaking in the bulk,provides a natural dark matter candidate. This is the lightest Kaluza-Kleinparticle odd under a certain discrete Z_2 symmetry, which has been introducedto improve the naturalness of the model, and resembles KK-parity but is lessconstraining. The dark matter candidate is the first KK mode of a 5D gauge field andelectroweak bounds force its mass above the TeV scale. Its pair annihilationrate is too small to guarantee the correct relic abundance; howevercoannihilations with colored particles greatly enhance the effectiveannihilation rate, leading to realistic relic densities.