Measurement of the angular coefficients in Z-boson events using electron and muon pairs from data taken at √s = 8 TeV with the ATLAS detector

Aad, G. and Abbott, B. and Abdallah, J. and Abdinov, O. and Abeloos, B. and Krasznahorkay, Attila and Pásztor, Gabriella and Tóth, József (2016) Measurement of the angular coefficients in Z-boson events using electron and muon pairs from data taken at √s = 8 TeV with the ATLAS detector. JOURNAL OF HIGH ENERGY PHYSICS (8). ISSN 1126-6708

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Abstract

The angular distributions of Drell–Yan charged lepton pairs in the vicinity of the Z-boson mass peak probe the underlying QCD dynamics of Z-boson production. This paper presents a measurement of the complete set of angular coefficients A0−7 describing these distributions in the Z-boson Collins–Soper frame. The data analysed correspond to 20.3 fb−1 of pp col- lisions at √s = 8 TeV, collected by the ATLAS detector at the CERN LHC. The measure- ments are compared to the most precise fixed-order calculations currently available (O(α2 s )) and with theoretical predictions embedded in Monte Carlo generators. The measurements are precise enough to probe QCD corrections beyond the formal accuracy of these calcula- tions and to provide discrimination between different parton-shower models. A significant deviation from the O(α2 s ) predictions is observed for A0 − A2. Evidence is found for non- zero A5,6,7, consistent with expectations.

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