Hidden Sector Dark Matter and the Galactic Center Gamma-Ray Excess: A
  Closer Look
  Stringent constraints from direct detection experiments and the Large Hadron
Collider motivate us to consider models in which the dark matter does not
directly couple to the Standard Model, but that instead annihilates into hidden
sector particles which ultimately decay through small couplings to the Standard
Model. We calculate the gamma-ray emission generated within the context of
several such hidden sector models, including those in which the hidden sector
couples to the Standard Model through the vector portal (kinetic mixing with
Standard Model hypercharge), through the Higgs portal (mixing with the Standard
Model Higgs boson), or both. In each case, we identify broad regions of
parameter space in which the observed spectrum and intensity of the Galactic
Center gamma-ray excess can easily be accommodated, while providing an
acceptable thermal relic abundance and remaining consistent with all current
constraints. We also point out that cosmic-ray antiproton measurements could
potentially discriminate some hidden sector models from more conventional dark
matter scenarios.
