A new approach for detecting compressed bino/wino at the LHC

In some supersymmetric models like split supersymmetry or models with non-universal gaugino mass, bino (LSP) and winos (NLSP) may have rather small mass splitting in order to provide the correct dark matter relic density through bino/wino co-annihilation. 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 $pp \to j \tildeχ^0_2 \tildeχ^\pm_1$ followed by $\tildeχ^0_2 \to γ\tildeχ^0_1$ and $\tildeχ^\pm_1 \to W^{*}\tildeχ^0_1\to \ell^\pm ν\tildeχ^0_1$ (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 $ΔM \sim 5-15$ GeV between bino (LSP) and wino (NLSP), the 14 TeV LHC with luminosity of 500$fb^{-1}$ can probe the wino up to 150 GeV (the sensitivity can reach $5σ$ for $ΔM = 5$ GeV and $2σ$ for $ΔM = 15$ 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 wino below 150 GeV allowed by relic density and the LUX limits.

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