LHC constraints on electroweakino dark matter revisited

We revisit LHC searches for heavy invisible particles by exploiting QCD initial state radiation. We recast a dijet signal region in a general multijet plus MET search by ATLAS. We find that the nontrivial mass limit can be obtained for various models of the electroweakino sector with the present data in hadronic channels. The winos are bound to be heavier than mW similar to > 160 GeV and Higgsinos mh similar to > 100 GeV, depending on the chargino-neutralino mass splitting. The expected exclusion limits at the LHC Run 3 with L 1/4 300 fb-1 increase to mW similar to > 200 GeV and mh similar to > 130 GeV for winos and Higgsino, respectively. This is the first LHC limit for promptly decaying nearly mass-degenerate winos.