Strong tW Scattering at the LHC

TL;DR

This paper explores how high-energy top quark scattering processes at the LHC can reveal deviations in top electroweak couplings, providing a new way to test models with strong top-sector interactions beyond current constraints.

Contribution

It introduces a novel approach to probe non-standard top-$Z$ couplings at the LHC through detailed analysis of $tW o tW$ scattering and proposes dedicated searches to improve sensitivity.

Findings

Derived the strongest direct bounds on $Ztt$ couplings to date.

Recast a CMS analysis at 8 TeV to constrain top electroweak interactions.

Designed a new search strategy at 13 TeV for $tar{t}Wj$ production.

Abstract

Deviations of the top electroweak couplings from their Standard Model values imply that certain amplitudes for the scattering of third generation fermions and longitudinally polarized vector bosons or Higgses diverge quadratically with momenta. This high-energy growth is a genuine signal of models where the top quark is strongly coupled to the sector responsible for electroweak symmetry breaking. We propose to profit from the high energies accessible at the LHC to enhance the sensitivity to non-standard top-$Z$ couplings, which are currently very weakly constrained. To demonstrate the effectiveness of the approach, we perform a detailed analysis of $tW \to tW$ scattering, which can be probed at the LHC via $pp\to t\bar{t}Wj$. By recasting a CMS analysis at 8 TeV, we derive the strongest direct bounds to date on the $Ztt$ couplings. We also design a dedicated search at 13 TeV that exploits the distinctive features of the $t\bar{t}Wj$ signal. Finally, we present other scattering processes in the same class that could provide further tests of the top-Higgs sector.