Evidence for the charge asymmetry in pp → t¯t production at √s = 13 TeV with the ATLAS detector

Inclusive and differential measurements of the top–antitop (t¯t) charge asym-
metry At¯tC and the leptonic asymmetry A`¯`C are presented in proton–proton collisions at √s = 13 TeV recorded by the ATLAS experiment at the CERN Large Hadron Collider. The measurement uses the complete Run 2 dataset, corresponding to an integrated luminosity of 139 fb−1, combines data in the single-lepton and dilepton channels, and employs reconstruction techniques adapted to both the resolved and boosted topologies. A Bayesian
unfolding procedure is performed to correct for detector resolution and acceptance effects. The combined inclusive t¯t charge asymmetry is measured to be At¯tC = 0.0068 ± 0.0015, which differs from zero by 4.7 standard deviations. Differential measurements are performed as a function of the invariant mass, transverse momentum and longitudinal boost of the t¯t system. Both the inclusive and differential measurements are found to be compatible with the Standard Model predictions, at next-to-next-to-leading order in quantum
chromodynamics perturbation theory with next-to-leading-order electroweak corrections. The measurements are interpreted in the framework of the Standard Model effective field theory, placing competitive bounds on several Wilson coefficients.