Constraining resonant dark matter with combined LHC electroweakino searches

In the Minimal Supersymmetric Standard Model light neutralinos can satisfy the dark matter (DM) abundance constraint by resonant annihilation via a $Z$ or a light Higgs ($h$) boson. In this work we study the current and future status of this scenario by investigating relevant experimental constraints, including DM direct detection, measurements of $Z$ and Higgs invisible decays, and direct searches at the Large Hadron Collider (LHC). To take full advantage of the LHC data, we combine the results of all relevant electroweakino searches performed by the Compact Muon Solenoid (CMS) Collaboration. Such combination increases the bound on the Higgsino mass parameter to $|\mu|>390$ GeV, which is about 80 GeV stricter than the bound obtained from individual analyses. In a simplified model we find that the $Z$ funnel region is on the brink of exclusion, the $h$ funnel for $\mu<0$ only survives if $\tan\beta<7.4$, and the $h$ funnel for $\mu>0$ is the main surviving region. Future DM direct detection experiments, such as LUX and ZEPLIN, can explore the whole region, while the high luminosity LHC can exclude $\tan\beta>8$ for $\mu>0$ and $\tan\beta>5.5$ for $\mu<0$. After applying the muon anomalous magnetic moment constraint only a tiny part of the $Z/h$ funnel region survives which will soon be probed by ongoing experiments.