Light neutralinos with large scattering cross sections in the minimal supersymmetric standard model

Motivated by recent data from CoGeNT and the DAMA annual modulation signal, we discuss collider constraints on the minimal supersymmetric standard model neutralino dark matter with mass in the 5-15 GeV range. The lightest superpartner (LSP) would be a bino with a small Higgsino admixture. Maximization of the dark matter nucleon scattering cross section for such a weakly interacting massive particle requires a light Higgs boson with tanβ enhanced couplings. Limits on the invisible width of the Z boson, combined with the rare decays B^±→τν, and the ratio B→Dτν/B→D ν, constrain cross sections to be below σn 5×10^-42cm2. This indicates a higher local dark matter density than is usually assumed by a factor of roughly 6 necessary to explain the CoGeNT excess. This scenario also requires a light charged Higgs boson, which can give substantial contributions to rare decays such as b→sγ and t→bH⁺. We also discuss the impact of Tevatron searches for Higgs bosons at large tan β.