Hunting Quasi-Degenerate Higgsinos

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We present a new strategy to uncover light, quasi-degenerate Higgsinos, a likely ingredient in a natural supersymmetric model. Our strategy focuses on Higgsinos with inter-state splittings of O(5-50) GeV that are produced in association with a hard, initial state jet and decay via off-shell gauge bosons to two or more leptons and missing energy, pp → j + MET + 2+ ℓ. The additional jet is used for triggering, allowing us to significantly loosen the lepton requirements and gain sensitivity to small inter-Higgsino splittings. Focusing on the two-lepton signal, we find the seemingly large backgrounds from diboson plus jet, tt and Z/γ* + j can be reduced with careful cuts, and that fake backgrounds appear minor. For Higgsino masses mχ just above the current LEP II bound (μ≃ 110) GeV we find the significance can be as high as 3 sigma at the LHC using the existing 20 fb⁻¹ of 8 TeV data. Extrapolating to LHC at 14 TeV with 100 fb⁻¹ data, and as one example M₁ = M₂ = 500 GeV, we find 5 sigma evidence for mχ 140 GeV and 2 sigma evidence for mχ 200 GeV. We also present a reinterpretation of ATLAS/CMS monojet bounds in terms of degenerate Higgsino (δmχ ≪ 5) GeV plus jet production. We find the current monojet bounds on mχ are no better than the chargino bounds from LEP II.