Unitarity and monojet bounds on models for DAMA, CoGeNT, and CRESST-II

If dark matter interacts with quarks or gluons, the mediator of these interactions is either directly accessible at the LHC or is so heavy that its effects are encoded in contact operators. We find that the self-consistency of a contact operator description at the LHC implies bounds on the mediator scale stronger than those found from missing energy searches. This translates into spin-independent elastic scattering cross sections at a level 10^-41 cm², with direct implications for the DAMA, CoGeNT, and CRESST-II anomalies. We then carefully explore the potential of monojet searches in the light mediator limit, focusing on a Z^' model with arbitrary couplings to quarks and dark matter. We find that Tevatron data currently provide the most stringent bounds for dark matter and Z^' masses below 100 GeV, and that these searches can constrain models for the DAMA, CoGeNT, and CRESST-II anomalies only if the mediator can decay to a pair of dark matter particles.