Aad G.Abbott B.Abbott D. C.Abeling K.Abidi S. H.Aboulhormae A.Abramowicz H.Abreu H.Abulaiti Y.Abusleme Hoffmana A. C.Acharyaa B. S.Bourdarios C. AdamAdamczyka L.Adamek L.Addepalli S. V.Adelman J.Adiguzelc A.Adorni S.Adye T.Affolder A. A.Afik Y.Agaras M. N.Agarwalaa J.Aggarwal A.Agheorghieseic C.Aguilar-Saavedraf J. A.Ahmad A.Ahmadov F.Ahmed W. S.Ahuja S.Ai X.Aiellia G.Tamlihate M. AitAitbenchikh B.Aizenberg I.Akbiyik M.Akesson T. P. A.Akimov A. V.Al Khoury K.Alberghib G. L.2025-05-192025-05-192023/08/100370-2693http://dx.doi.org/10.1016/j.physletb.2023.137829https://publicacionesabiertas.userena.cl/handle/123456789/224A measurement of the polarisation of Wbosons produced in top-quark decays is presented, using proton-proton collision data at a centre-of-mass energy of v s= 13TeV. The data were collected by the ATLAS detector at the Large Hadron Collider and correspond to an integrated luminosity of 139fb(-1). The measurement is performed selecting t tevents decaying into final states with two charged leptons (electrons or muons) and at least two b-tagged jets. The polarisation is extracted from the differential cross-section distribution of the cos theta* variable, where theta(*) is the angle between the momentum direction of the charged lepton from the Wboson decay and the reversed momentum direction of the b-quark from the top-quark decay, both calculated in the Wboson rest frame. Parton-level results, corrected for the detector acceptance and resolution, are presented for the cos theta* angle. The measured fractions of longitudinal, left- and right-handed polarisation states are found to be f(0) = 0.684 +/- 0.005 (stat.)+/- 0.014 (syst.), f(L)= 0.318 +/- 0.003 (stat.)+/- 0.008 (syst.) and f(R)=-0.002 +/- 0.002 (stat.)+/- 0.014 (syst.), in agreement with the Standard Model prediction. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).PAIR PRODUCTION, PLUS PLUSArticle