Measurements of top-quark pair to Z-boson cross-section ratios at √s=13, 8, 7 TeV with the ATLAS detector. / The ATLAS Collaboration.

In: Journal of High Energy Physics, Vol. 2017, 117, 02.2017, p. 1-54.

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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√s for the two processes and at different s√s for each process, as well as double ratios of the two processes at different s√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.
Original languageEnglish
Article number117
Pages (from-to)1-54
Number of pages54
JournalJournal of High Energy Physics
Volume2017
Early online date23 Feb 2017
DOIs
Publication statusPublished - Feb 2017
This open access research output is licenced under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

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