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 non-trivial 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 $m_{\tilde{W}}\gtrsim 160$ GeV and higgsinos $m_{\tilde{h}}\gtrsim 100$ GeV, depending on the chargino-neutralino mass splitting. The expected exclusion limits at the LHC Run 3 with $\mathcal{L}=300$ fb${}^{-1}$ increase to $m_{\tilde{W}}\gtrsim 200$ GeV and $m_{\tilde{h}}\gtrsim 130$ GeV for winos and higgsino, respectively. This is the first LHC limit for promptly decaying nearly mass-degenerate winos.