@article{00e6cfff8a9140da815c689f259548dc,
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 Allbrooke, {B. M.M.} and Allen, {B. W.} and T. Kaji and N. Kimura and T. Mitani and M. Morinaga and K. Yorita",
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",
publisher = "Springer New York",
number = "4",
}