Combined collider constraints on neutralinos and charginos
  Searches for supersymmetric electroweakinos have entered a crucial phase, as
the integrated luminosity of the Large Hadron Collider is now high enough to
compensate for their weak production cross-sections. Working in a framework
where the neutralinos and charginos are the only light sparticles in the
Minimal Supersymmetric Standard Model, we use gambit to perform a detailed
likelihood analysis of the electroweakino sector. We focus on the impacts of
recent ATLAS and CMS searches with 36 fb$^{-1}$ of 13 TeV proton-proton
collision data. We also include constraints from LEP and invisible decays of
the $Z$ and Higgs bosons. Under the background-only hypothesis, we show that
current LHC searches do not robustly exclude any range of neutralino or
chargino masses. However, a pattern of excesses in several LHC analyses points
towards a possible signal, with neutralino masses of $(m_{\tilde{\chi}_1^0},
m_{\tilde{\chi}_2^0}, m_{\tilde{\chi}_3^0}, m_{\tilde{\chi}_4^0})$ = (8-155,
103-260, 130-473, 219-502) GeV and chargino masses of
$(m_{\tilde{\chi}_1^{\pm}}, m_{\tilde{\chi}_2^{\pm}})$ = (104-259, 224-507) GeV
at the 95% confidence level. The lightest neutralino is mostly bino, with a
possible modest Higgsino or wino component. We find that this excess has a
combined local significance of $3.3\sigma$, subject to a number of cautions. If
one includes LHC searches for charginos and neutralinos conducted with 8 TeV
proton-proton collision data, the local significance is lowered to 2.9$\sigma$.
We briefly consider the implications for dark matter, finding that the correct
relic density can be obtained through the Higgs-funnel and $Z$-funnel
mechanisms, even assuming that all other sparticles are decoupled. All samples,
gambit input files and best-fit models from this study are available on Zenodo.
