New approach for detecting a compressed bino/wino at the LHC

In some supersymmetric models like split supersymmetry or models with nonuniversal gaugino mass, `bino [lightest sparticle (LSP)] and wino [next-to-lightest sparticle (NLSP)] may have rather small mass splitting in order to provide the correct dark matter relic density through bino/wino coannihilation. Such a scenario with the compressed bino/wino is difficult to explore at the LHC. In this work we propose to probe this scenario from pp→jχ₂⁰χ₁^± followed by χ₂⁰→γχ₁⁰ and ${{{}}{{χ}}}₁^{±{}}{→}{W}*{{{}}{{χ}}}₁⁰{→}{{}}^{±{}}{ν}{{{}}{{χ}}}₁⁰$ (this method is also applicable to the compressed bino/Higgsino scenario). Through a detailed Monte Carlo simulation for both the signal and the backgrounds, we find that for a mass splitting ${{Δ}}M{~}10--15 GeV$ between bino (LSP) and wino (NLSP), the 14 TeV LHC with a luminosity of $1000 {fb}^{{-}1}$ can probe the wino up to 150 GeV (the sensitivity can reach $3.4{σ}$ for ${{Δ}}M=10 GeV$ and $2{σ}$ for ${{Δ}}M=15 GeV$). We also investigate the dark matter detection sensitivities for this scenario and find that the planned XENON-1T (2017) cannot fully cover the parameter space with a wino below 150 GeV allowed by relic density and the LUX limits.