Using effective operators to understand CoGeNT and CDMS-Si signals

Several direct detection experiments have reported positive signals consistent with a dark matter particle with a mass of approximately 7-9 GeV and a spin-independent scattering cross section of 2.5-4.8 x 10(-41) cm(2). These results do not rise to the level of discovery, but assuming that they are due to dark matter, some questions about the underlying physics can already be addressed. In this paper, I apply the effective operator formalism for dark matter Standard Model interactions to the results of the CoGeNT and CDMS silicon target experiments. I demonstrate that only one set of flavor-blind effective operators between dark matter and quarks can be consistent with the reported results in all energy regimes of interest, namely thermal freeze-out, nuclear scattering, indirect detection, and TeV-scale colliders. This set of operators implies large couplings of dark matter with heavy quarks. The alternative implies either that the new physics has nontrivial flavor structure, that the effective formalism is not applicable and so contains new states in the spectrum accessible at the LHC, or has large annihilation channels (possibly via effective operators) into noncolored Standard Model particles.