Scalar versus fermionic top partner interpretations of $t\bar t + E_T^{\rm miss}$ searches at the LHC

TL;DR

This paper evaluates how existing LHC searches for supersymmetry in the top-antitop plus missing energy final state constrain models with fermionic top partners and dark matter, finding that current searches exclude masses up to about 850 GeV.

Contribution

The study demonstrates that efficiency maps from stop-neutralino models can be applied to fermionic top partner models and provides new efficiency maps for high-mass top partners.

Findings

Masses up to approximately 850 GeV are excluded for fermionic top partners.

Efficiency of SUSY searches is similar for scalar and fermionic top partners.

New efficiency maps are provided for high-mass top partner searches.

Abstract

We assess how different ATLAS and CMS searches for supersymmetry in the $t\bar t + E_T^{\rm miss}$ final state at Run 1 of the LHC constrain scenarios with a fermionic top partner and a dark matter candidate. We find that the efficiencies of these searches in all-hadronic, 1-lepton and 2-lepton channels are quite similar for scalar and fermionic top partners. Therefore, in general, efficiency maps for stop-neutralino simplified models can also be applied to fermionic top-partner models, provided the narrow width approximation holds in the latter. Owing to the much higher production cross-sections of heavy top quarks as compared to stops, masses up to $m_T\approx 850$ GeV can be excluded from the Run 1 stop searches. Since the simplified-model results published by ATLAS and CMS do not extend to such high masses, we provide our own efficiency maps obtained with CheckMATE and MadAnalysis 5 for these searches. Finally, we also discuss how generic gluino/squark searches in multi-jet final states constrain heavy top partner production.