Naturally resonant dark matter from extra dimensions

We explore the mass-resonance structure that naturally arises in extradimensional models. The resonance can enhance both dark matter annihilation and self-interactions. We demonstrate such a resonance structure by considering the fermionic dark matter and dark photon models on an <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msup> <a:mi>S</a:mi> <a:mn>1</a:mn> </a:msup> <a:mo>/</a:mo> <a:mo stretchy="false">(</a:mo> <a:msub> <a:mi>Z</a:mi> <a:mn>2</a:mn> </a:msub> <a:mo>×</a:mo> <a:msubsup> <a:mi>Z</a:mi> <a:mn>2</a:mn> <a:mo>′</a:mo> </a:msubsup> <a:mo stretchy="false">)</a:mo> </a:math> orbifold. We also note that this model embeds a dark matter axial-vector coupling to the dark photon, thereby opening up the viable dark matter parameter space. We then present the unique predictions for direct-detection experiments and accelerator searches.