Formation of the ηc in two-photon collisions at LEP

M Acciarri,L Lista,E Fiandrini,P Lecomte,F Cindolo,L Merola,S Wynhoff,M Maity,M Kräber,C Sciacca,M Diemoz,A Arefiev,A Doria,P Levtchenko,B Borgia,M Rescigno,M Wadhwa,L Baksay,N Cavallo,G Vesztergombi,W Lustermann,I Iashvili,T Moulik,A Böhm,D Ruschmeier,C Tully,L Luminari,L Malgeri,J Quartieri,G Sultanov,F.C Erné,A Vorvolakos,M Kaur,J Kirkby,J Fay,B Bertucci,F Ziegler,D Haas,A Biland,U Becker,S Cucciarelli,W Kittel,A Nisati,G Marian,M Chamizo,G Ambrosi,K Riles,P Lecoq,L Servoli,B Cozzoni,F Marzano,T Ferguson,C Palomares,S Shevchenko,G Passaleva,G Chen,S Banerjee,L Tauscher,J Schwenke,P Extermann,R De Asmundis,T Aziz,T Siedenburg,M Bourquin,M Dittmar,N Shivarov,K Mazumdar,B Stoyanov,G Coignet,D Son,P Bartalini,G Carlino,M Pedace,G Organtini,A Hervé,S Reucroft,C Paus,I Vodopianov,M Wang,L Taylor,L Romero,A Buijs,M Felcini,V Plyaskin,P Duinker,D Prokofiev,P Paolucci,D Pandoulas,F Cavallari,G Landi,N Raja,A Rosca,I Vorobiev,M Napolitano,C Luci,L Cifarelli,G Schwering,J Hirschfelder,S Vlachos,T Paul,F Ferroni,S Braccini,I Korolko,A De Salvo,A Chen,G Viertel,D Kiss,D Hatzifotiadou,M Lebeau,K Deiters,M Gataullin,D Mangeol,C Schäfer,Samuel C.C Ting,I Josa-Mutuberrı́A,H Hofer,I Fisk,N Produit,A Robohm,G Chiefari,P Marchesini,R Van Gulik,P Hidas,H Schopper,Y Uchida,P Denes,V Pojidaev,D Luckey,A Buffini,L Fredj,M Cerrada,P Lebrun,E Shumilov,M Campanelli,S Mele,P Achard,F Di Lodovico,A Aloisio,A Klimentov,F Denotaristefani,P Le Coultre,C Cecchi,G Castellini,D Piccolo,D Van Dierendonck,R Ramelli,D Della Volpe,A Bay,J Busenitz,K Sudhakar,D Ren,J Ulbricht,H Rykaczewski,A Balandras,S Falciano,M Steuer,F Anselmo,D Bourilkov,M Basile,H Vogt,J Mnich,M Von Der Mey,S Sarkar,G Cara Romeo,A Weber,O Grimm,F Cotorobai,G Raven,J Salicio,H Nowak,J Berdugo,M Vivargent,W Lohmann,J Casaus,G Zilizi,A Engler,N Gheordanescu,E Valente,S Giagu,P Bagnaia,G Alemanni,J Tóth,D Peach,A Gurtu,A Favara,D Vicinanza,H El Mamouni,H Vogel,T Van Rhee,M Chemarin,N Colino,L Barone,K Freudenreich,M Biasini,J Alcaraz,R Ostonen,I Clare,E Longo,C Dionisi,H Anderhub,T Angelescu,O Adriani,K Lassila-Perini,R Faccini,R Battiston,A Hasan,A Button,G Grenier,W Wallraff,G Rahal-Callot,S Pensotti,F Behner,J Allaby,D Kim,D Duchesneau,D Dufournand,H Suter,D Perret-Gallix,M Pieri,F Muheim,C Timmermans,A Kunin,C Furetta,S Schmidt-Kaerst,A Stone,W Krenz,P.G Rancoita,L Lugnier,L Xia,T Azemoon,F Filthaut,E Pistolesi,P De Jong,G Holzner,G Mirabelli,V Koutsenko,V Shoutko,M Pauluzzi,P Wienemann,K Lübelsmeyer,M Pohl,C Li,A Zichichi,A Degré,S Costantini,P Berges,M Weber,D Schmitz,I Vetlitsky,A Seganti,J Pothier,S Patricelli,A Straessner,R Barillère,B De La Cruz,R Clare,S Riemann,S Villa,M Meschini,J Rodin,C Civinini,T Hebbeker,H Fesefeldt,Yu Galaktionov,F Becattini,H Postema,M Capell,B Monteleoni,A Barczyk,A Shvorob,A Dominguez,S Paoletti,D Sciarrino,S Gentile,D Kamrad,F Cesaroni,A Lebedev,R Leiste,J B Ye ,Y S Lu ,B N Jin ,B P Roe ,S M Ting ,U K Chaturvedi ,T Nießen ,D Stickland ,Z A Liu ,Y D Oh ,A A Vorobyov ,H S Chen ,P Ladrón De Guevara ,F Pauß ,Virendra K Gupta ,V Brigljević ,L W Jones ,R W Kraemer ,M A Falagán ,G Y Zhu ,D H Kim ,S X Wu ,Péter Molnár ,S N Ganguli ,X L Wang ,S C Yeh ,Bryan Smith ,S Blyth ,O L Fedin ,S C Kim ,G B Mohanty ,H R Hoorani ,T Dai ,Michel Fabre ,Gennaro De Pascale ,Z Szillási ,А Малинин ,H G Wilkens ,Y J Pei ,J A Van Dalen ,Saptaparna Bhattacharya ,S S Gau ,Min Yang ,Z M Wang ,C Mañá ,Howard A Stone ,Á Csilling ,G M Chen ,Imad Baptiste Laktineh ,M N Kienzle‐Focacci ,H J Lee ,J D Swain ,V Andreev ,R Y Zhu ,R A Khan ,F J Eppling ,J J Blaising ,G Massaro ,P Piroué ,R C Ball ,R D’alessandro ,Emanuele Leonardi ,P Garcı́a-Abia ,Y Zalite ,S C Tonwar ,J A Rubio ,M Aguilar-Benı́tez ,L Boldizsár ,A C König ,J G Branson ,G J Bobbink ,Y H Chang ,A Zalite ,J M You ,G Forconì ,M P Sanders ,K L Tung ,B A Petersen ,Z F Gong ,J M Le Goff ,B L Betev ,M G Alviggi ,A M Cartacci ,B Z Yang ,A K Kopp ,L Z Sun ,W G ,J P Martin ,C H Lin ,I Durán ,X D Cai ,M E Sarakinos ,M W Gruenewald ,E Sánchez ,M T Dova ,X Chéreau ,D J Schotanus ,P H Fisher ,C G Yang ,H J Yang ,F Nessi‐Tedaldi ,H F Chen ,H B Newman ,M A Rahaman ,V A Schegelsky ,P Lacenter ,Z P Zhang ,P A Razis ,J H Field ,W J Metzger ,A J.m Muijs ,П Спиллантини ,W J Burger ,X W Tang ,P Déglon ,I H Park ,J K Kim ,G S Muanza ,W Lin ,R R Mcneil ,L Gutay ,Z Z Xu ,F M Brochu ,S Hou ,H K Park ,A P Colijn ,F Linde ,J D Burger ,S Rosier‐Lees ,Margot Zöller

doi:10.1016/s0370-2693(99)00784-4

Abstract

The two-photon width Γ γγ of the η c meson has been measured with the L3 detector at LEP. The η c is studied in the decay modes π + π − π + π −, π + π −K +K −, K 0 s K ± π ∓, K +K − π 0, π + π − η, π + π − η′, and ρ + ρ − using an integrated luminosity of 140 pb −1 at s ≃91 GeV and of 52 pb −1 at s ≃183 GeV. The result is Γ γγ(η c)=6.9±1.7 stat±0.8 sys±2.0 (BR) keV. The Q 2 dependence of the η c cross section is studied for Q 2<9 GeV 2. It is found to be better described by a Vector Meson Dominance model form factor with a J-pole than with a ρ-pole. In addition, a signal of 29±11 events is observed at the χ c0 mass. Upper limits for the two-photon widths of the χ c0, χ c2, and η c ′ are also given.

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