It has recently been shown that dark-matter annihilation to bottom quarks provides a good fit to the galactic-center gamma-ray excess identified in the Fermi-LAT data .
In the favored dark matter mass range m \sim 30 - 40 GeV , achieving the best-fit annihilation rate \sigma v \sim 5 \times 10 ^ { -26 } cm ^ { 3 } s ^ { -1 } with perturbative couplings requires a sub-TeV mediator particle that interacts with both dark matter and bottom quarks .
In this paper , we consider the minimal viable scenarios in which a Standard Model singlet mediates s -channel interactions only between dark matter and bottom quarks , focusing on axial-vector , vector , and pseudoscalar couplings .
Using simulations that include on-shell mediator production , we show that existing sbottom searches currently offer the strongest sensitivity over a large region of the favored parameter space explaining the gamma-ray excess , particularly for axial-vector interactions .
The 13 TeV LHC will be even more sensitive ; however , it may not be sufficient to fully cover the favored parameter space , and the pseudoscalar scenario will remain unconstrained by these searches .
We also find that direct-detection constraints , induced through loops of bottom quarks , complement collider bounds to disfavor the vector-current interaction when the mediator is heavier than twice the dark matter mass .
We also present some simple models that generate pseudoscalar-mediated annihilation predominantly to bottom quarks .