Naturally Resonant Dark Matter from Extra Dimensions

We explore the mass resonance structure that naturally arises from extra-dimensional models. The resonance can enhance the dark matter annihilation as well as self-interaction. We demonstrate such a resonance structure by considering the fermionic dark matter and dark photon models on an $S^1\mathrm{/}(Z_2\times Z_2^{\mathrm{\prime }})$ orbifold. We also note that this model embeds dark matter axial vector coupling to the dark photon, which opens up the viable dark matter parameter space. We then present the unique predictions for direct-detection experiments and accelerator searches.