Differential top-antitop cross-section measurements as a function of observables constructed from final-state particles using pp collisions at √s = 7TeV in the ATLAS detector

Aad, G and Abbott, B. and Abdallah, J. and Abdel Khalek, S. and Abdinov, O. and Aben, R. and Abi, B., The ATLAS collaboration (2015) Differential top-antitop cross-section measurements as a function of observables constructed from final-state particles using pp collisions at √s = 7TeV in the ATLAS detector. Journal of High Energy Physics, 2015 (100). ISSN 1029-8479

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    Abstract

    Various differential cross-sections are measured in top-quark pair (tt¯) events produced in proton-proton collisions at a centre-of-mass energy of s√=7 TeV at the LHC with the ATLAS detector. These differential cross-sections are presented in a data set corresponding to an integrated luminosity of 4.6 fb−1. The differential cross-sections are presented in terms of kinematic variables, such as momentum, rapidity and invariant mass, of a top-quark proxy referred to as the pseudo-top-quark as well as the pseudo-top-quark pair system. The dependence of the measurement on theoretical models is minimal. The measurements are performed on tt¯ events in the lepton+jets channel, requiring exactly one charged lepton and at least four jets with at least two of them tagged as originating from a b-quark. The hadronic and leptonic pseudo-top-quarks are defined via the leptonic or hadronic decay mode of the W boson produced by the top-quark decay in events with a single charged lepton. Differential cross-section measurements of the pseudo-top-quark variables are compared with several Monte Carlo models that implement next-to-leading order or leading-order multi-leg matrix-element calculations.