Differential measurements of $\bar{t}tZ$ and $\bar{t}t\bar{t}t$ at large $Q^2$ at FCC-hh

Abstract

This contribution presents studies of differential top-quark measurements at the Future Circular Collider in its proton-proton stage (FCC-hh). The analyses target the leptonic final states of the $\bar{t}tZ$ and $\bar{t}t\bar{t}t$ production processes. Particular focus is given to the high-$Q^2$ regime, where sensitivity to new physics, as encoded in an Effective Field Theory framework, is enhanced. The dataset corresponds to an integrated luminosity of 30 ${\text{ab}}^{-1}$ at $\sqrt{s}=84$ TeV. The reconstructed transverse momentum ${\text{p}}_{\text{T}}(Z_{\ell \ell })$ distribution is shown to be measurable up to approximately 2 TeV with a precision of 20% in the high energy region (${\text{p}}_{\text{T}}(Z_{\ell \ell })$ >1.8 TeV). The scalar transverse momentum ${\text{H}}_{\text{T}}$ of the four-top production reaches 3.5 TeV with a precision of 35%. Additionally, a dedicated study of the lepton reconstruction efficiency shows that redefining the isolation variable to account for the highly boosted objects at FCC-hh improves the total signal yield in $\bar{t}tZ$ by a factor of 1.5.

Poster at the 18th International Workshop on Top Quark Physics (Top2025), 21-26 September 2025