New angular and other cuts to improve the Higgsino signal at the LHC
Howard Baer, V. Barger, Dibyashree Sengupta, Xerxes Tata
Abstract
Motivated by the fact that naturalness arguments strongly suggest that the supersymmetry (SUSY)-preserving Higgsino mass parameter $\ensuremath{\mu}$ cannot be too far above the weak scale, we reexamine Higgsino pair production in association with a hard QCD jet at the High Luminosity LHC. We focus on ${\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}+{\overline{)E}}_{T}+j$ events from the production and subsequent decay, ${\stackrel{\texttildelow{}}{\ensuremath{\chi}}}_{2}^{0}\ensuremath{\rightarrow}{\stackrel{\texttildelow{}}{\ensuremath{\chi}}}_{1}^{0}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$, of the heavier neutral Higgsino. The novel feature of our analysis is that we suggest angular cuts to reduce the important background from $Z(\ensuremath{\rightarrow}\ensuremath{\tau}\ensuremath{\tau})+j$ events more efficiently than the ${m}_{\ensuremath{\tau}\ensuremath{\tau}}^{2}<0$ cut that has been used by the ATLAS and CMS Collaborations. Other cuts, needed to reduce backgrounds from $t\overline{t}$, $WWj$, and $W/Z+\ensuremath{\ell}\overline{\ensuremath{\ell}}$ production, are also delineated. We plot out the reach of LHC14 for 300 and $3000\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ and also show distributions that serve to characterize the Higgsino signal, noting that Higgsinos may well be the only superpartners accessible at LHC14 in a well-motivated class of natural SUSY models.