TY  - JOUR
T1  - Measurements of top-quark pair to \(Z\)-boson cross-section ratios at \(\sqrt{s}\) \(=13 , 8, 7\) TeV with the ATLAS detector
T2  - Journal of High Energy Physics
N2  - Ratios of top-quark pair to \(Z\)-boson cross sections measured from proton-proton collisions at the LHC centre-of-mass energies of \(\sqrt{s}\) = 13 TeV, 8 TeV, and 7 TeV are presented by the ATLAS Collaboration. Single ratios, at a given \(\sqrt{s}\) for the two processes and at different \(\sqrt{s}\) for each process, as well as double ratios of the two processes at different \(\sqrt{s}\), are evaluated. The ratios are constructed using previously published ATLAS measurements of the \({t\overline{t}}\) 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 \(\sqrt{s}\) = 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 \(\sqrt{s}\) 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.
KW  - High energy physics
KW  - Hadron-Hadron scattering (experiments)
Y1  - 2017
UR  - https://opus.bibliothek.uni-wuerzburg.de/opus4-wuerzburg/frontdoor/index/index/docId/17354
UR  - https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-173544
VL  - 2017
IS  - 02
ER  -