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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, 2017; 77(4):264-1-264-28
Publisher: Springer
Issue Date: 2017
ISSN: 1434-6044
Statement of
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
RMID: 0030071628
DOI: 10.1140/epjc/s10052-017-4819-4
Appears in Collections:Physics publications

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