Measurement of the W boson polarisation in t(t)over-barevents from pp collisions at √s=8 TeV in the lepton plus jets channel with ATLAS



Aaboud, M, Aad, G, Abbott, B, Abdallah, J, Abdinov, O, Abeloos, B, AbouZeid, OS, Abraham, NL, Abramowicz, H, Abreu, H
et al (show 2840 more authors) (2017) Measurement of the W boson polarisation in t(t)over-barevents from pp collisions at √s=8 TeV in the lepton plus jets channel with ATLAS EUROPEAN PHYSICAL JOURNAL C, 77 (4). 264-. ISSN 1434-6044, 1434-6052

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Abstract

This paper presents a measurement of the polarisation of W bosons from tt¯ 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.

Item Type: Article
Additional Information: 42 pages in total, author list starting page 26, 6 figures, 5 tables, published in EPJC. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2016-02. v3 includes modifications described in the erratum that can be found at https://link.springer.com/article/10.1140%2Fepjc%2Fs10052-018-6520-7
Uncontrolled Keywords: ATLAS Collaboration
Depositing User: Symplectic Admin
Date Deposited: 15 Jun 2017 10:34
Last Modified: 22 May 2026 22:37
DOI: 10.1140/epjc/s10052-017-4819-4
Related Websites:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3007994
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