Study of prompt photon production in hadronicZ 0 decays

M Reale,M Gandelman,C Lacasta,J Medbo,C Walck,L Roos,N I Zimin,T Lesiak,J Hrubec,C Defoix,D Wicke,G Barbiellini,A Seitz,A Normand,L K Resvanis,F J Harris,M Dris,T L Hessing,E I Rosenberg,M Battaglia,A Stocchi,C Matteuzzi,G Valenti,J M Lopez,W Ruckstuhl,N Demaria,M Mc Cubbin,A Trombini,P Roudeau,I Roncagliolo,S Simonetti,N Neumeister,N Pukhaeva,M Pimenta,F Naraghi,M Bozzo,D Reid,I Ajinenko,K Kurvinen,F Simonetto,D Souza-Santos,L Lanceri,M Baubillier,M Caccia,M Kaiser,F Parodi,B Åsman,A Ferrer,M A Lopez Aguera,C Parkes,P Kokkinias,I Siccama,P Chliapnikov,F Richard,P Siegrist,R Leitner,R Nicolaidou,O Tchikilev,Z Krumstein,J P Tavernet,C Bricman,L Lyons,V Nikolaenko,A C Benvenuti,B A Khomenko,A N Sisakian,I Last,W Neumann,C Kreuter,J Strauss,M Sannino,J Chauveau,P Privitera,W Krupinski,M Feindt,D Y Bardin,G Sajot,E Rosso,U Mjoernmark,N Ershaidat,F Fulda-Quenzer,M V Castillo Gimenez,P Rebecchi,M Hahn,F Carena,A Klovning,D Liko,P Sponholz,U Amaldi,P Collins,V Uvarov,L S Vertogradov,B Golob,M 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Smirnov,V Vrba,K Hultqvist,B Erzen,M R Monge,Z Hajduk,E Vlasov,F Cao,F Hahn,R Sosnowski,M Weierstall,C Meroni,V Kostioukhine,F Verbeure,J Dolbeau,V Hedberg,O Ullaland,S J Alvsvaag,Y Sacquin,P Kubinec,K Doroba,B Ueberschaer,M Elsing,V Lapin,R Contri,F Fontanelli,G Tristram,M Pernicka,E Fokitis,A Ruiz,A Lopez-Fernandez,P Zalewski,M Blume,M Zito,G Eigen,P Poropat,E Graziani,H Mueller,F Mandl,W Oberschulte-Beckmann,J Guy,P Ioannou,E Karvelas,S Tzamarias,D Z Toet,T Moa,D Fassouliotis,T Todorov,Y Sedykh,P Frenkiel,V Gracco,E Spiriti,E Vallazza,F Ledroit,W J Murray,H T Phillips,N J Kjaer,A Romero,P Juillot,T J V Bowcock,J Salt,P Jarry,W Bartl,P Negri,F Bianchi,B Stugu,A Lipniacka,G Vegni,S Squarcia,R C Shellard,L Chaussard,M S Bilenky,M Tyndel,H B Crawley,D W Lane,L Mirabito,T Burgsmueller,A Cattai,A Daum,M Michelotto,D Crennell,R Moeller,P Billoir,S Plaszczynski,R Sekulin,A Perrotta,R Lindner,P Morettini,A Petrolini,J Timmermans,P Vincent,H Dijkstra,L G Tkatchev,O Podobrin,P Lutz,O 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Ruhlmann-Kleider,M Szeptycka,H Wahlen,C Zacharatou,L Gerdyukov,D Gamba,Y Dufour,O Kouznetsov,A M Segar,J L Contreras,I A Tyapkin,F R Cavallo,J N Jackson,N Vassilopoulos,M Paganoni,A Firestone,A Tomaradze,B Franek,A Nomerotski,K Woschnagg,H Klein,P J Holt,P Antilogus,S Navas,J Lemonne,A L Read,S Lamblot,M Berggren,C Caso,M Dracos,P Branchini,N N Khovanski,J Macnaughton,F Formenti,M Wielers,M Gibbs,G Zumerle,A Zalewska,K D Brand,J A Barrio,W Bonivento,E Cortina,V Chabaud,H Rahmani,W Hao,L Tortora,A Onofre,L Ventura,M Górski ,S O Holmgren ,Yu Belokopytov ,W K Van Doninck ,R Keränen ,S Němeček ,P Fischer ,K Cankoçak ,P Jałocha ,J J Hernández ,J P Engel ,J Gerber ,Th D Papadopoulou ,J Lämsä ,L Mundim ,J C Marin ,T Bologneşe ,P Beillière ,Yu Gouz ,L Di Ciaccio ,D Radojičić ,M L Turluer ,T Ekelöf ,J M Brunet ,M Dönszelmann ,P Kramer ,G P Gopal ,J P Laugier ,J Loken ,M A E Schyns ,Erik Johansson ,A De Angelis ,Α Μάρκου ,H Pałka ,S Marti-Garcia ,L Jönsson ,E Higón ,G Chelkov ,J Sánchez ,D Gelé ,G Della Ricca ,J Van Eldik ,Florent Dupont ,M Lokajı́ček ,Imad Baptiste Laktineh ,M Esṕırito Santo ,J Wickens ,O Bärring ,A M Zaitsev ,Ch La Vaissière ,F Barão ,B De Lotto ,M Günther ,Aurelio Juste Rozas ,J Królikowski ,A Vodopyanov ,W Mitaroff ,E Dahl‐Jensen ,B Tomé ,G W Van Apeldoorn ,J Cuevas ,B T King ,L De Paula ,P Brückman ,P Van Dam ,P.s.l Booth ,P Dauncey ,C De Clercq ,J M Vizan Garcia ,Rui Henriques ,P Renton ,K A Drees ,C Stănescu ,Ph Charpentier ,P Jönsson ,S De Brabandere ,W De Boer ,D Žontar ,E Katsoufis ,P Pagès ,V M Ronjin ,V Lefébure ,J E Augustin ,B Sitár ,D Blöch ,K Österberg ,G Tranströmer ,R Frühwirth ,W D Apel ,R Brenner ,F Martínez-Vidal ,Daniel Bertrand ,B Maréchal ,J Řídký ,R.c.a Brown ,B Jean‐Marie ,S R Hahn ,S Czellár ,N Redaelli ,Kathy Huet ,J Rameš ,G Wilkinson ,C Garćıa ,C De Saint-Jean ,W Vénus ,H De Boeck ,Ph Gavillet ,A De Min ,C Martínez-Rivero ,G Mæhlum ,K H Becks

doi:10.1007/bf02907381

Abstract

From a sample of 1.5 millionZ 0→qq decays collected by the DELPHI detector during 1991, 1992 and 1993, the production cross section for isolated final state photons is measured and is compared with theO(α, α s) matrix element calculations implemented in the EEPRAD and GNJETS Monte Carlo generators. The observed photon yield is used to derive the electroweak couplings of charge 2/3 (u-type) and charge 1/3 (d-type) quarks to theZ 0 boson. The measured valuesc 2/3=0.91 −0.36 +0.25 andc 1/3=1.62 −0.17 +0.24 are compatible with the Standard Model prediction,c 2/3=1.145 andc 1/3=1.477.

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