Evidence for the charge asymmetry in $pp\to t\bar{t}$ production at $\sqrt{s}=13$ TeV with the ATLAS detector

Abstract

Inclusive and differential measurements of the top-antitop ($t\bar{t}$) charge asymmetry $A_{\text{C}}^{t\bar{t}}$ and the leptonic asymmetry $A_{\text{C}}^{\ell \bar{\ell }}$ are presented in proton-proton collisions at $\sqrt{s}=13$ 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 $t\bar{t}$ charge asymmetry is measured to be $A_{\text{C}}^{t\bar{t}}=0.0068\pm 0.0015$, 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 $t\bar{t}$ 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.

arXiv comment67 pages in total, 22 figures, 14 tables, submitted to JHEP. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2020-06

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