Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/115083
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Type: Journal article
Title: Measurement of the W boson polarisation in tt¯ events from pp collisions at √s = 8 TeV in the lepton + jets channel with ATLAS
Other Titles: Measurement of the W boson polarisation in tt -bar events from pp collisions at root s = 8 TeV in the lepton + jets channel with ATLAS
Author: Aaboud, M.
Aad, G.
Abbott, B.
Abdallah, J.
Abdinov, O.
Abeloos, B.
AbouZeid, O.
Abraham, N.
Abramowicz, H.
Abreu, H.
Abreu, R.
Abulaiti, Y.
Acharya, B.
Adachi, S.
Adamczyk, L.
Adams, D.
Adelman, J.
Adomeit, S.
Adye, T.
Affolder, A.
et al.
Citation: European Physical Journal C: Particles and Fields, 2017; 77(4):264-1-264-28
Publisher: Springer
Issue Date: 2017
ISSN: 1434-6044
1434-6052
Statement of
Responsibility: 
M. Aaboud ... P. Jackson ... L. Lee ... A. Petridis ... M.J. White ... [et al.] (The ATLAS Collaboration)
Abstract: This paper presents a measurement of the polarisation of W bosons from t¯t decays, reconstructed in events with one high-pT lepton and at least four jets. Data from pp collisions at the LHC were collected at √s = 8 TeV and correspond to an integrated luminosity of 20.2 fb⁻¹. The angle θ* between the b-quark from the top quark decay and a direct W boson decay product in the W boson rest frame is sensitive to the W boson polarisation. Two different W decay products are used as polarisation analysers: the charged lepton and the down-type quark for the leptonically and hadronically decaying W boson, respectively. The most precise measurement of the W boson polarisation via the distribution of cos θ* is obtained using the leptonic analyser and events in which at least two of the jets are tagged as b-quark jets. The fitted fractions of longitudinal, left- and right-handed polarisation states are F0 = 0.709 ± 0.019, FL = 0.299 ± 0.015 and FR = −0.008 ± 0.014, and are the most precisely measured W boson polarisation fractions to date. Limits on anomalous couplings of the Wtb vertex are set.
Keywords: ATLAS Collaboration
Rights: © CERN for the benefit of the ATLAS collaboration 2017. This article is an open access publication. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecomm ons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Funded by SCOAP3.
DOI: 10.1140/epjc/s10052-017-4819-4
Grant ID: ARC
Published version: http://dx.doi.org/10.1140/epjc/s10052-017-4819-4
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