Direct and indirect detection and LHC signals of bino-Higgsino dark matter

Abstract

If the lightest dark matter neutralino has a sufficiently large Higgsino component, its spin-independent and spin-dependent cross sections on nucleons can be sizable enough to be detected soon in direct and indirect surveys. We outline in this paper some characteristic features expected of mixed bino-Higgsino dark matter. If the observed relic density is saturated by the bino-Higgsino dark matter, it fixes the amount of allowable bino-Higgsino mixing and provides predictions for other observables which can be tested at the Large Hadron Collider (LHC). We study the correlation between the cross sections and the branching ratio of ${B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$. For a mixed bino-Higgsino dark matter, the mass differences of the neutralinos can be less than ${M}_{Z}$. This will cause an excess of lepton pairs, above the standard model predictions, from the decays of the two heavier neutralinos. We discuss implications of the dilepton invariant mass distribution, and outline a way to extract the neutralino parameters for testing gaugino mass unification and deducing the relic density from an interplay of astrophysical detection and LHC measurements.