%0 Journal Article
%T Measurement of the W boson polarisation in t(t)over-barevents from pp collisions at root s=8 TeV in the lepton plus jets channel with ATLAS
%A ATLAS Collaboration (Aaboud, M. et al
%A Alvarez Piqueras, D.
%A Barranco Navarro, L.
%A Cabrera Urban, S.
%A Castillo Gimenez, V.
%A Cerda Alberich, L.
%A Costa, M. J.
%A Fernandez Martinez, P.
%A Ferrer, A.
%A Fiorini, L.
%A Fuster, J.
%A Garcia, C.
%A Garcia Navarro, J. E.
%A Gonzalez de la Hoz, S.
%A Higon-Rodriguez, E.
%A Jimenez Pena, J.
%A King, M.
%A Lacasta, C.
%A Mamuzic, J.
%A Marti-Garcia, S.
%A Melini, D.
%A Mitsou, V. A.
%A Pedraza Lopez, S.
%A Rodriguez Rodriguez, D.
%A Romero Adam, E.
%A Ros, E.
%A Salt, J.
%A Sanchez Martinez, V.
%A Soldevila, U.
%A Sanchez, J.
%A Valero, A.
%A Valls Ferrer, J. A.
%A Vos, M.
%J European Physical Journal C
%D 2017
%V 77
%N 4
%I Springer
%@ 1434-6044
%G English
%F ATLASCollaborationAaboud_etal2017
%O WOS:000400235900001
%O exported from refbase (https://references.ific.uv.es/refbase/show.php?record=3133), last updated on Fri, 02 Jun 2017 14:49:20 +0000
%X This paper presents a measurement of the polarisation of W bosons from t (t) over bar t 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 root s = 8 TeV and correspond to an integrated luminosity of 20.2 fb(-1). The angle theta* 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 theta* 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 F-0 = 0.709 +/- 0.019, F-L = 0.299 +/- 0.015 and F-R = – 0.008 +/- 0.014, and are the most precisely measured W boson polarisation fractions to date. Limits on anomalous couplings of the W tb vertex are set.
%R 10.1140/epjc/s10052-017-4819-4
%U http://arxiv.org/abs/1612.02577
%U https://doi.org/10.1140/epjc/s10052-017-4819-4
%P 264-28pp