Same-sign Higgsino Production at the CERN LHC: How Not to Hunt for Natural Supersymmetry

TL;DR

This paper analyzes the potential for detecting light higgsinos via same-sign W boson fusion at the LHC, concluding that the production cross section is too small for effective searches in natural SUSY models.

Contribution

It demonstrates that same-sign higgsino production via vector boson fusion is highly suppressed due to an emergent symmetry, making this channel ineffective for natural SUSY detection.

Findings

Cross section for same-sign higgsino pairs is less than 0.02 fb.

Emergent U(1) symmetry suppresses higgsino production.

Channel is not viable for natural SUSY searches at LHC.

Abstract

We examine the prospects for detecting light charged higgsinos that are expected to be a necessary feature of natural SUSY models via $pp\to {\widetilde W}^\pm{\widetilde W}_1^\pm jj+X$ processes arising dominantly from $W^\pm W^\pm$ fusion at LHC13. The signal will be a pair of same-sign leptons ($e$ or $\mu$) in events with two relatively forward, hemispherically-separated jets with a large rapidity gap. We find that even though the higgsinos have a full-strength $SU(2)$ gauge couplings to $W$-bosons, the LHC13 cross section for the production of same sign higgsino pairs is smaller than 0.02 fb over most of the interesting range of natural SUSY parameters, even before leptonic branching fractions of the chargino are included. This cross section is strongly suppressed because the two neutral Majorana higgsinos can be combined into a single Dirac neutralino if the bino and the winos are much heavier than the higgsinos, as is the case in natural SUSY models: in this limit, higgsino couplings to $W$-bosons exhibit an emergent (approximate) $U(1)_{\rm ino}$ global symmetry that suppresses same sign higgsino production by vector boson fusion. We conclude that this channel is not a viable way to search for natural SUSY even at the high luminosity upgrade of the Large Hadron Collider.