Taking aim at the wino-higgsino plane with the LHC

TL;DR

This paper develops an improved LHC search strategy for higgsino and mixed higgsino-wino states in the MSSM, projecting the potential to exclude large parts of the natural wino-higgsino parameter space at high luminosities.

Contribution

It introduces a novel search method using a joint likelihood analysis with a hadronically tagged vector boson, enhancing sensitivity to higgsino-wino states in the MSSM.

Findings

Sensitivity to higgsino-like states up to 550 GeV.

Sensitivity to mixed states above 300 GeV.

Full HL-LHC run can exclude much of the natural wino-higgsino parameter space.

Abstract

In this work we explore multiple search strategies for higgsinos and mixed higgsino-wino states in the MSSM and project the results onto the $(\mu,M_2)$ plane. Assuming associated production of higgsino-like pairs with a $W/Z$ boson, we develop a search in a channel characterized by a hadronically tagged vector boson accompanied by missing energy. We use as our template an ATLAS search for dark matter produced in association with a hadronically decaying vector boson, but upgrade the search by implementing a joint likelihood analysis, binning the missing transverse energy distribution, which greatly improves the search sensitivity. For higgsino-like states (more than 96% admixture) we find sensitivity to masses up to 550 GeV. For well-mixed higgsino-wino states (70-30% higgsino) we still find sensitivities above 300 GeV. Using this newly proposed search, we draw a phenomenological map of the wino-higgsino parameter space, recasting several complementary searches for disappearing tracks, soft leptons, trileptons, and hadronic diboson events in order to predict LHC coverage of the $(\mu,M_2)$ mass plane at integrated luminosities of up to $3\,\text{ab}^{-1}$. Altogether, the full run of the HL-LHC can exclude much of the "natural" ($\mu,M_2 <$ 500 GeV) wino-higgsino parameter space.