Measurement of the top quark pair production charge asymmetry in proton-proton collisions at root √s = 7 TeV using the ATLAS detector

Aad, G. and Abajyan, T. and Abbott, B. and Abdallah, J. and Khalek, S. A. and Abdinov, O. and Aben, R. and Abi, B. and Abolins, M. and AbouZeid, O. S. and Abramowicz, H. and Abreu, H. and Abulaiti, Y. and Acharya, B. S. and Adamczyk, L. and Adams, D. L. and Addy, T. N. and Adelman, J. and Adomeit, S. and Adye, T. and Aefsky, S. and Agatonovic-Jovin, T. and Aguilar-Saavedra, J. A. and Agustoni, M. and Ahlen, S. P. and Ahmad, A. and Ahmadov, F. and Aielli, G. and Akesson, T. P. A. and Akimoto, G. and Krasznahorkay, Attila and Nagai, Yoshikazu and Pásztor, Gabriella and Tóth, József (2014) Measurement of the top quark pair production charge asymmetry in proton-proton collisions at root √s = 7 TeV using the ATLAS detector. JOURNAL OF HIGH ENERGY PHYSICS (2). ISSN 1126-6708

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Abstract

This paper presents a measurement of the top quark pair (t¯t) production charge asymmetry AC using 4.7 fb−1 of proton–proton collisions at a centre–of–mass energy √s = 7 TeV collected by the ATLAS detector at the LHC. A t¯t-enriched sample of events with a single lepton (electron or muon), missing transverse momentum and at least four high transverse momentum jets, of which at least one is tagged as coming from a b–quark, is selected. A likelihood fit is used to reconstruct the t¯t event kinematics. A Bayesian unfolding procedure is employed to estimate AC at the parton–level. The measured value of the t¯t production charge asymmetry is AC = 0.006 ± 0.010, where the uncertainty includes both the statistical and the systematic components. Differential AC measurements as a function of the invariant mass, the rapidity and the transverse momentum of the t¯t–system are also presented. In addition, AC is measured for a subset of events with large t¯t velocity, where physics beyond the Standard Model could contribute. All measurements are consistent with the Standard Model predictions.

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