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.

67 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

References in corpus (28)

• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• An Introduction to PYTHIA 8.2
• Parton distributions for the LHC
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• New parton distributions for collider physics
• Herwig++ Physics and Manual
• Parton distributions in the LHC era: MMHT 2014 PDFs
• A parton shower algorithm based on Catani-Seymour dipole factorisation
• Single-top Wt-channel production matched with parton showers using the POWHEG method
• -- HATHOR -- HAdronic Top and Heavy quarks crOss section calculatoR
• Single-top hadroproduction in association with a W boson
• The Catchment Area of Jets
• HATHOR for single top-quark production: Updated predictions and uncertainty estimates for single top-quark production in hadronic collisions
• How bright is the proton? A precise determination of the photon parton distribution function
• Top, Higgs, Diboson and Electroweak Fit to the Standard Model Effective Field Theory
• The Photon Content of the Proton
• A Monte Carlo global analysis of the Standard Model Effective Field Theory: the top quark sector
• Top Quarks, Axigluons and Charge Asymmetries at Hadron Colliders
• Effective-Field-Theory Approach to Top-Quark Production and Decay
• Next-to-leading-order predictions for t-channel single-top production at hadron colliders
• Automated one-loop computations in the SMEFT
• Single top quark production at LHC with anomalous Wtb couplings
• Constraining heavy colored resonances from top-antitop quark events
• Probing the Tevatron t tbar asymmetry at LHC
• Top quark asymmetry from a non-Abelian horizontal symmetry
• Massive color-octet bosons and the charge asymmetries of top quarks at hadron colliders
• Asymmetries in top quark pair production at hadron colliders
• Using Final State Pseudorapidities to Improve s-channel Resonance Observables at the LHC

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