Hunting quasidegenerate Higgsinos

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 $O(5\ensuremath{-}50)\text{ }\text{ }\mathrm{GeV}$ 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, $pp\ensuremath{\rightarrow}j+{\overline{)E}}_{T}+{2}^{+}\ensuremath{\ell}$. 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 $Z/{\ensuremath{\gamma}}^{*}+j$ can be reduced with careful cuts, and that fake backgrounds appear minor. For Higgsino masses ${m}_{\ensuremath{\chi}}$ just above the current LEP II bound ($\ensuremath{\mu}\ensuremath{\simeq}110\text{ }\text{ }\mathrm{GeV}$) we find the significance can be as high as $3\ensuremath{\sigma}$ at the LHC using the existing $20\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of 8 TeV data. Extrapolating to LHC at 14 TeV with $100\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data, and as one example ${M}_{1}={M}_{2}=500\text{ }\text{ }\mathrm{GeV}$, we find $5\ensuremath{\sigma}$ evidence for ${m}_{\ensuremath{\chi}}\ensuremath{\lesssim}140\text{ }\text{ }\mathrm{GeV}$ and $2\ensuremath{\sigma}$ evidence for ${m}_{\ensuremath{\chi}}\ensuremath{\lesssim}200\text{ }\text{ }\mathrm{GeV}$. We also present a reinterpretation of ATLAS/CMS monojet bounds in terms of degenerate Higgsino ($\ensuremath{\delta}{m}_{\ensuremath{\chi}}\ensuremath{\ll}5\text{ }\text{ }\mathrm{GeV}$) plus jet production. We find the current monojet bounds on ${m}_{\ensuremath{\chi}}$ are no better than the chargino bounds from LEP II.