Achard, P.Adriani, O.Aguilar-Benitez, M.Alcaraz, J.Alemanni, G.Allaby, J.Aloisio, A.Alviggi, M.G.Anderhub, H.Andreev, V.P.Anselmo, F.Arefiev, A.Azemoon, T.Aziz, T.Bagnaia, P.Bajo, A.Baksay, G.Baksay, L.Baldew, S.V.Banerjee, S.Banerjee, Sw.Barczyk, A.Barillère, R.Bartalini, P.Basile, M.Batalova, N.Battiston, R.Bay, A.Becattini, F.Becker, U.Behner, F.Bellucci, L.Berbeco, R.Berdugo, J.Berges, P.Bertucci, B.Betev, B.L.Biasini, M.Biglietti, M.Biland, A.Blaising, J.J.Blyth, S.C.Bobbink, G.J.Böhm, A.Boldizsar, L.Borgia, B.Bottai, S.Bourilkov, D.Bourquin, M.Braccini, S.Branson, J.G.Brochu, F.Burger, J.D.Burger, W.J.Cai, X.D.Capell, M.Romeo, G.C.Carlino, G.Cartacci, A.Casaus, J.Cavallari, F.Cavallo, N.Cecchi, C.Cerrada, M.Chamizo, M.Chang, Y.H.Chemarin, M.Chen, A.Chen, G.Chen, G.M.Chen, H.F.Chen, H.S.Chiefari, G.Cifarelli, L.Cindolo, F.Clare, I.Clare, R.Coignet, G.Colino, N.Costantini, S.De la Cruz, B.Cucciarelli, S.Van Dalen, J.A.De Asmundis, R.Déglon, P.Debreczeni, J.Degré, A.Dehmelt, K.Deiters, K.Della Volpe, D.Delmeire, E.Denes, P.DeNotaristefani, F.De Salvo, A.Diemoz, M.Dierckxsens, M.Dionisi, C.Dittmar, M.Doria, A.2010-11-052010-11-052010-11-05200310.1016/S0370-2693(03)00172-22-s2.0-0037417186https://infoscience.epfl.ch/handle/20.500.14299/56913The three different helicity states of W bosons produced in the reaction e+e- → W+W- → lvqq̄′ at LEP are studied using leptonic and hadronic W decays. Data at centre-of-mass energies √s = 183-209 GeV are used to measure the polarisation of W bosons, and its dependence on the W boson production angle. The fraction of longitudinally polarised W bosons is measured to be 0.218 ± 0.027 ± 0.016 where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model expectation. © 2003 Published by Elsevier Science B.V.text::journal::journal article::research article