Study of W-boson polarisations and triple gauge boson couplings in the reaction e+e-→W+W- at LEP 2

J Abdallah,L Di Ciaccio,G Valenti,T Spassov,G Myatt,N Van Remortel,P Tortosa,F Richard,A Hallgren,M Ellert,T Lesiak,W Mitaroff,J Lemonne,M Trochimczuk,N Amapane,P Jarry,B De Lotto,J Cuevas,U Schwickerath,A Zalewska,Ph Charpentier,O Smirnova,G Jarlskog,L Lyons,R Monge,U Parzefall,G Cosme,A Onofre,O Passon,V Zhuravlov,G Della Ricca,M Begalli,T Rovelli,A Stocchi,A Petrolini,J Marco,M Chapkin,S Amato,M Mazzucato,F Pierre,M Blom,N Pukhaeva,R Contri,T Da Silva,M Bonesini,V Pozdniakov,J Salt,R Marco,R Gokieli,G Wilkinson,H Wahlen,B Stugu,A Ouraou,E Migliore,A Malek,P Tyapkin,V Verzi,G Grosdidier,K Muenich,P Kluit,M Boonekamp,E Piotto,J Chudoba,J Piedra,D Treille,M Paganoni,J D’Hondt,M Witek,P Morettini,M Battaglia,D Liko,O Kouznetsov,S Katsanevas,M Szeptycka,A Ballestrero,D Wicke,A Ferrer,V Obraztsov,J Guy,C Weiser,P Chliapnikov,S Maltezos,P Antilogus,M Winter,K Grzelak,C De Clercq,K Nawrocki,R Orava,R Sosnowski,A Zintchenko,P Baillon,V Vrba,M Margoni,L Salmi,G Polok,M Hennecke,J Drees,W De Boer,M Pimenta,F Cossutti,E Ben-Haim,C Parkes,L Pape,F Ferro,L De Paula,C Meroni,D Crennell,J Montenegro,F Tegenfeldt,A Savoy-Navarro,P Checchia,G Fanourakis,L Jungermann,N Mastroyiannopoulos,C Mariotti,W Liebig,J Rehn,M Kucharczyk,B Golob,Y Arnoud,A Di Simone,F Veloso,U Mjoernmark,S Paiano,K Hamacher,C Kourkoumelis,P Collins,O Yushchenko,A Passeri,F Fulda-Quenzer,S Tzamarias,V Poireau,P Verdier,P Lutz,J Hoffman,F Mazzucato,T Szumlak,D Zavrtanik,W Adam,V Lepeltier,T Allmendinger,L Pieri,M Elsing,K Doroba,L Vitale,A Perrotta,T Podobnik,A Tonazzo,B Muryn,C Matteuzzi,M Calvi,M Baubillier,B Buschbeck,R Mc Nulty,D Loukas,P Kokkinias,A Van Lysebetten,A Lipniacka,J Fuster,A De Angelis,T Camporesi,M Szczekowski,R Leitner,D Vilanova,Z Krumstein,A Behrmann,M Mulders,F Kapusta,S Ask,T Tabarelli,R Reinhardt,V Hedberg,M Rivero,J Wickens,I Van Vulpen,P Renton,M Nassiakou,M Bluj,G Kernel,A Oyanguren,P Bambade,Ph Gavillet,L Peralta,R Barbier,P Roudeau,A Andreazza,D Reid,G Tristram,J Macnaughton,A Sopczak,J Strauss,A Sadovsky,A Romero,A Sokolov,B Bouquet,K Hamilton,P Rebecchi,G Leder,E Brodet,V Canale,D Ryabtchikov,P Buschmann,J Van Eldik,N Anjos,R Nicolaidou,U Flagmeyer,C Haag,L Mundim,F Carena,S Haug,H Foeth,P.S.L Booth,G Vegni,V Perepelitsa,G Borisov,S Todorovova,R Brenner,T Moa,A Baroncelli,M Feindt,F Hauler,F Parodi,N Besson,W Da Silva,M Gandelman,K Moenig,A Pullia,M Siebel,R Chierici,O Botner,D Moraes,P Zalewski,E Katsoufis,F Mandl,F Ledroit,V Uvarov,G Eigen,F Matorras,E Graziani,N De Maria,C Sander,L Leinonen,P Abreu,E Fokitis,C Troncon,U Kerzel,V Ruhlmann-Kleider,R Sekulin,A De Min,T Myklebust,M Nikolenko,E Anashkin,D Fassouliotis,C Joram,A Augustinus,M Moch,N Benekos,S Andringa,D Jeans,P Ronchese,U Amaldi,J Timmermans,P Van Dam,M Tobin,G Smadja,M Berggren,E N Gazis ,B T King ,B Maréchal ,M Houlden ,J Jackson ,C Bérat ,M Costa ,U Muêller ,Josh Cuevas Fernandez ,S U Chung ,J Mašík ,J E Augustin ,Thomas Albrecht ,C Martínez-Rivero ,K H Becks ,S O Holmgren ,N I Zimin ,A N Sisakian ,N F Castro ,B Tomé ,P P Allport ,P Gonçalves ,Erik Johansson ,N J Kjaer ,C García ,P Jönsson ,T J V Bowcock ,P Adžić ,R Alemany–Fernández ,D Blöch ,J H Lopes ,M L Turluer ,A Obłąkowska-Mucha ,D Radojičić ,S Carrillo Moreno ,M E Pol ,A G Olshevski ,J M Lopez ,B P Kerševan ,H Pałka ,K Cieślik ,Α Μάρκου ,J Palacios ,J C Marin ,J Lämsä ,I A Tyapkin ,J Řídký ,D Y Bardin ,M M Stanitzki ,D Rodríguez ,A Washbrook ,Daniel Bertrand ,M Besançon ,T Ekelöf ,B Åsman ,P J Holt ,F R Cavallo ,Th D Papadopoulou ,P Trávníc̆ek ,W J Murray ,A C Benvenuti ,M C Espírito Santo ,G J Barker ,W Vénus ,I R Boyko ,P Brückman ,F L Navarria ,M Bračko ,K F Read ,J M Brunet ,K Österberg ,L G Tkatchev ,G Gómez-Ceballos ,W D Apel ,J Rameš ,M Župan

doi:10.1140/epjc/s10052-008-0528-3

Abstract

A determination of the single W Spin Density Matrix (SDM) elements in the reaction e+e- -> W+W- -> l nu q qbar (l=e/mu) is reported at centre-of-mass energies between 189 and 209 GeV. The data sample used corresponds to an integrated luminosity of 520 pb^{-1} taken by DELPHI between 1998 and 2000. The single W SDM elements, rho_{tau tau'}^{W+-} (tau,tau' = +/-1 or 0), are determined as a function of the W- production angle with respect to the e- beam direction and are obtained from measurements of the W decay products by the application of suitable projection operators, Lambda_{tau tau'}, which assume the V-A coupling of the W boson to fermions. The measured SDM elements are used to obtain the fraction of longitudinally polarised Ws, with the result: sigma_L/sigma_tot = 24.9 +/- 4.5(stat) +/- 2.2(syst) % at a mean energy of 198 GeV. The SDM elements are also used to determine the Triple Gauge Couplings Delta g_1^Z, Delta kappa_gamma, lambda_gamma and g_4^Z, ~kappa_Z and ~lambda_Z. For the CP-violating couplings the results of single parameter fits are: g_4^Z = -0.39 +0.19 -0.20 ~kappa_Z = -0.09 +0.08 -0.05 ~lambda_Z = -0.08 +/- 0.07 . The errors are a combination of statistical and systematic errors. All results are consistent with the Standard Model.

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