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

The ATLAS collaboration

doi:10.1140/epjc/s10052-017-4819-4

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

The ATLAS collaboration

Mohamed I University
Aix-Marseille Université
University of Oklahoma
University of Texas at Arlington
Azerbaijan National Academy of Sciences
IN2P3/CNRS
University of California at Santa Cruz
University of Sussex
Tel Aviv University
Technion-Israel Institute of Technology
University of Oregon
Stockholm University
Oskar Klein Centre
National Institute for Nuclear Physics
Abdus Salam International Centre for Theoretical Physics
King's College London
The University of Tokyo
AGH University of Krakow
United States Department of Energy
Northern Illinois University
Ludwig Maximilian University of Munich
Rutherford Appleton Laboratory
University of Belgrade
Laboratório de Instrumentação e Física Experimental de Partículas
University of Granada
Boston University
Joint Institute for Nuclear Research
University of Rome Tor Vergata
Lund University
P.N. Lebedev Physical Institute of the Russian Academy of Sciences
University of Bologna
University of Victoria BC
Université Grenoble Alpes
Universidad Nacional de La Plata
CERN
Horia Hulubei National Institute of Physics and Nuclear Engineering
National Technical University of Athens
Czech Technical University in Prague
University of Salento
The University of Chicago
Columbia University

Research output: Contribution to journal › Article › peer-review

56 Scopus citations

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.

Original language	English
Article number	264
Journal	European Physical Journal C
Volume	77
Issue number	4
DOIs	https://doi.org/10.1140/epjc/s10052-017-4819-4
State	Published - Apr 1 2017

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@article{a599207dc2ff488ea472eda96a402625,

title = "Measurement of the W boson polarisation in tt¯ events from pp collisions at √s = 8 TeV in the lepton + jets channel with ATLAS",

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.",

author = "\{The ATLAS collaboration\} and M. Aaboud and G. Aad and B. Abbott and J. Abdallah and O. Abdinov and B. Abeloos and AbouZeid, \{O. S.\} and Abraham, \{N. L.\} and H. Abramowicz and H. Abreu and R. Abreu and Y. Abulaiti and Acharya, \{B. S.\} and S. Adachi and L. Adamczyk and Adams, \{D. L.\} and J. Adelman and S. Adomeit and T. Adye and Affolder, \{A. A.\} and T. Agatonovic-Jovin and Aguilar-Saavedra, \{J. A.\} and Ahlen, \{S. P.\} and F. Ahmadov and G. Aielli and H. Akerstedt and {\AA}kesson, \{T. P.A.\} and Akimov, \{A. V.\} and Alberghi, \{G. L.\} and J. Albert and S. Albrand and \{Alconada Verzini\}, \{M. J.\} and M. Aleksa and Aleksandrov, \{I. N.\} and C. Alexa and G. Alexander and T. Alexopoulos and M. Alhroob and B. Ali and M. Aliev and G. Alimonti and J. Alison and Alkire, \{S. P.\} and H. Arnold and \{Da Via\}, C. and V. Dao and J. Hobbs and J. Jia and G. Piacquadio and D. Tsybychev",

note = "Publisher Copyright: {\textcopyright} 2017, CERN for the benefit of the ATLAS collaboration.",

year = "2017",

month = apr,

day = "1",

doi = "10.1140/epjc/s10052-017-4819-4",

language = "English",

volume = "77",

journal = "European Physical Journal C",

issn = "1434-6044",

number = "4",

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TY - JOUR

T1 - Measurement of the W boson polarisation in tt¯ events from pp collisions at √s = 8 TeV in the lepton + jets channel with ATLAS

AU - The ATLAS collaboration

AU - Aaboud, M.

AU - Aad, G.

AU - Abbott, B.

AU - Abdallah, J.

AU - Abdinov, O.

AU - Abeloos, B.

AU - AbouZeid, O. S.

AU - Abraham, N. L.

AU - Abramowicz, H.

AU - Abreu, H.

AU - Abreu, R.

AU - Abulaiti, Y.

AU - Acharya, B. S.

AU - Adachi, S.

AU - Adamczyk, L.

AU - Adams, D. L.

AU - Adelman, J.

AU - Adomeit, S.

AU - Adye, T.

AU - Affolder, A. A.

AU - Agatonovic-Jovin, T.

AU - Aguilar-Saavedra, J. A.

AU - Ahlen, S. P.

AU - Ahmadov, F.

AU - Aielli, G.

AU - Akerstedt, H.

AU - Åkesson, T. P.A.

AU - Akimov, A. V.

AU - Alberghi, G. L.

AU - Albert, J.

AU - Albrand, S.

AU - Alconada Verzini, M. J.

AU - Aleksa, M.

AU - Aleksandrov, I. N.

AU - Alexa, C.

AU - Alexander, G.

AU - Alexopoulos, T.

AU - Alhroob, M.

AU - Ali, B.

AU - Aliev, M.

AU - Alimonti, G.

AU - Alison, J.

AU - Alkire, S. P.

AU - Arnold, H.

AU - Da Via, C.

AU - Dao, V.

AU - Hobbs, J.

AU - Jia, J.

AU - Piacquadio, G.

AU - Tsybychev, D.

PY - 2017/4/1

Y1 - 2017/4/1

N2 - 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.

AB - 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.

UR - https://www.scopus.com/pages/publications/85018254033

U2 - 10.1140/epjc/s10052-017-4819-4

DO - 10.1140/epjc/s10052-017-4819-4

M3 - Article

AN - SCOPUS:85018254033

SN - 1434-6044

VL - 77

JO - European Physical Journal C

JF - European Physical Journal C

IS - 4

M1 - 264

ER -

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

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