Measurements of top-quark pair to Z-boson cross-section ratios at √s=13 , 8, 7 TeV with the ATLAS detector
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Date
2017
Authors
Aaboud, M.
Aad, G.
Abbott, B.
Abdallah, J.
Abdinov, O.
Abeloos, B.
Abidi, S.
AbouZeid, O.
Abraham, N.
Abramowicz, H.
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Journal article
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Journal of High Energy Physics (JHEP), 2017; 2017(2):117-1-117-54
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M. Aaboud, G. Aad, B. Abbott, J. Abdallah ... Paul D. Jackson … Martin White … et al. (ATLAS Collaboration)
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Abstract
Ratios of top-quark pair to Z-boson cross sections measured from proton-proton collisions at the LHC centre-of-mass energies of s√=13 TeV, 8 TeV, and 7 TeV are presented by the ATLAS Collaboration. Single ratios, at a given s√ for the two processes and at different s√ for each process, as well as double ratios of the two processes at different s√, are evaluated. The ratios are constructed using previously published ATLAS measurements of the tt¯ and Z-boson production cross sections, corrected to a common phase space where required, and a new analysis of Z → ℓ+ℓ− where ℓ = e, μ at s√=13 TeV performed with data collected in 2015 with an integrated luminosity of 3.2 fb−1. Correlations of systematic uncertainties are taken into account when evaluating the uncertainties in the ratios. The correlation model is also used to evaluate the combined cross section of the Z → e + e − and the Z → μ + μ − channels for each s√ value. The results are compared to calculations performed at next-to-next-to-leading-order accuracy using recent sets of parton distribution functions. The data demonstrate significant power to constrain the gluon distribution function for the Bjorken-x values near 0.1 and the light-quark sea for x < 0.02.
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© The Author(s) 2017. This article is published under an open access license. Please check the 'Copyright Information' section for details of this license and what re-use is permitted. If your intended use exceeds what is permitted by the license or if you are unable to locate the licence and re-use information, please contact the Rights and Permissions team.