Measurement of the W boson polarisation in tt[bar] events from pp collisions at √s = 8 TeV in the lepton + jets channel with ATLAS

This paper presents a measurement of the polarisation of W bosons from tt¯ decays, reconstructed in events with one high-p T 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 t...

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Main Authors: Aaboud, Morad (Author) , Anders, Christoph (Author) , Andrei, George Victor (Author) , Antel, Claire (Author) , Baas, Alessandra Edda (Author) , Brandt, Oleg (Author) , Djuvsland, Julia Isabell (Author) , Dunford, Monica (Author) , Ferreira de Lima, Danilo Enoque (Author) , Geisler, Manuel Patrice (Author) , Giulini, Maddalena (Author) , Hanke, Paul (Author) , Jongmanns, Jan (Author) , Kluge, Eike-Erik (Author) , Kolb, Mathis (Author) , Kretz, Moritz (Author) , Kugel, Andreas (Author) , Lang, Valerie (Author) , Lisovyi, Mykhailo (Author) , Meier, Karlheinz (Author) , Meyer zu Theenhausen, Hanno (Author) , Narrias Villar, Daniel Isaac (Author) , S̜ahinsoy, Merve (Author) , Schätzel, Sebastian (Author) , Scharf, Veit (Author) , Schöning, André (Author) , Schultz-Coulon, Hans-Christian (Author) , Sosa Corral, David E. (Author) , Stamen, Rainer (Author) , Starovoitov, Pavel (Author) , Suchek, Stanislav (Author) , Wessels, Martin (Author)
Corporate Author: ATLAS Collaboration (Author)
Format: Article (Journal)
Language:English
Published: 26 April 2017
In: The European physical journal. C, Particles and fields
Year: 2017, Volume: 77, Issue: 4
ISSN:1434-6052
DOI:10.1140/epjc/s10052-017-4819-4
Online Access:Verlag, Volltext: https://doi.org/10.1140/epjc/s10052-017-4819-4
Verlag: https://link.springer.com/article/10.1140/epjc/s10052-017-4819-4
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Author Notes:ATLAS Collaboration*
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Summary:This paper presents a measurement of the polarisation of W bosons from tt¯ decays, reconstructed in events with one high-p T 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 cosθ∗ 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.
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*ATLAS Collaboration: M. Aaboud, C.F. Anders, V. Andrei, C. Antel, A.E. Baas, O. Brandt, J.J. Djuvsland, M. Dunford, D.E. Ferreira de Lima, M.P. Geisler, M. Giulini, P. Hanke, J. Jongmanns, E.-E. Kluge, M. Kolb, M. Kretz, A. Kugel, V.S. Lang, M. Lisovyi, K. Meier, H. Meyer zu Theenhausen, D.I. Narrias Villar, M. Sahinsoy, S. Schaetzel, V. Scharf, A. Schoening, H.-C. Schultz-Coulon, D. Sosa, R. Stamen, P. Starovoitov, S. Suchek, M. Wessels [und 2818 weitere Personen]
Physical Description:Online Resource
ISSN:1434-6052
DOI:10.1140/epjc/s10052-017-4819-4