We present a new strategy to uncover light, quasidegenerate Higgsinos, a likely ingredient in a natural supersymmetric model. Our strategy focuses on Higgsinos with interstate splittings of $O(5-50)\mathrm{GeV}$ 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, $pp\to j+{\cancel{E}}_T+2^{+}\ell$. 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, $\overline{t}t$ and $Z/{\gamma }^{*}+j$ can be reduced with careful cuts, and that fake backgrounds appear minor. For Higgsino masses $m_{\chi }$ just above the current LEP II bound ($\mu \simeq 110\mathrm{GeV}$) we find the significance can be as high as $3\sigma$ at the LHC using the existing $20{\mathrm{fb}}^{-1}$ of 8 TeV data. Extrapolating to LHC at 14 TeV with $100{\mathrm{fb}}^{-1}$ of data, and as one example $M_1=M_2=500\mathrm{GeV}$, we find $5\sigma$ evidence for $m_{\chi }\lesssim 140\mathrm{GeV}$ and $2\sigma$ evidence for $m_{\chi }\lesssim 200\mathrm{GeV}$. We also present a reinterpretation of ATLAS/CMS monojet bounds in terms of degenerate Higgsino ($\delta m_{\chi }\ll 5\mathrm{GeV}$) plus jet production. We find the current monojet bounds on $m_{\chi }$ are no better than the chargino bounds from LEP II.

• Received 15 January 2014

DOI:https://doi.org/10.1103/PhysRevD.89.075007