New angular (and other) cuts to improve the higgsino signal at the LHC

Motivated by the fact that naturalness arguments strongly suggest that the SUSY-preserving higgsino mass parameter mu cannot be too far above the weak scale, we re-examine higgsino pair production in association with a hard QCD jet at the HL-LHC. We focus on l^+l^-+\eslt+j events from the production and subsequent decay, \tchi_2^0→\tchi_1^0l^+l^-, of the heavier neutral higgsino. The novel feature of our analysis is that we suggest angular cuts to reduce the important background from Z(→ττ)+j events more efficiently than the m_{ττ}^2<0 cut that has been used by the ATLAS and CMS collaborations. Other cuts, needed to reduce backgrounds from tt, WWj and W/Z+ll production, are also delineated. We plot out the reach of LHC14 for 300 and 3000~fb^{-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.