Observation of thehc(P11)State of Charmonium

Jonathan L Rosner ,D Urner,Z Metreveli,R Mountain,B Gittelman,K K Seth,R Gray,M Cravey,L Breva-Newell,K Randrianarivony,S B Athar,J Hietala,R Sia,C S Park,A J Sadoff,T K Pedlar,R S Galik,E H Thorndike,F Liu,S E Csorna,G Bonvicini,H Schwarthoff,Q He,N Menaa,B W Lang,S Blusk,G S Adams,M E Watkins,C Sedlack,J E Duboscq,N Lowrey,S Mehrabyan,I Karliner,W Park,E J White,H Muramatsu,R Nandakumar,D Peterson,R A Briere,D Riley,M Dubrovin,D L Kreinick,A H Mahmood,B Sanghi,P Naik,V Savinov,O Dorjkhaidav,D G Cassel,P Rubin,K Y Gao,V Pavlunin,J Kandaswamy,H Stoeck,G Tatishvili,M R Shepherd,J Napolitano,G D Gollin,D L Hartill,S A Dytman,S W Gray,M Weinberger,D Cinabro,J Pivarski,K W Edwards,V Potlia,S Stroiney,J P Alexander,H Mahlke-Krüger,T Klein,T E Coan,D T Gong,B K Heltsley,C Cawlfield,R Ehrlich,L Fields,B I Eisenstein,C Boulahouache,T Wilksen,D Hertz,D M Asner,A W Scott,R Redjimi,M Artuso,T Skwarnicki,D Kim,J P Cummings,A López ,H Vogel,C D Jones,D Besson,J Yelton,G S Huang,V Credé ,Y S Gao,P Zweber,J Chen,D Cronin-Hennessy,A Smith,I P J Shipsey,J E Ramirez Vargas ,I Danko,J Ernst,K M Ecklund,H Méndez ,Z Li,W Sun ,G P Chen,T O Meyer,W A Love ,R Patel,L Gibbons,James S Williams ,T Ferguson,J Wiss,M Selen,S Dobbs,P Avery,N Adam ,A Rýd ,X Shi,R Poling,В Е Кузнецов ,K Berkelman,J Muêller ,K M Weaver,H Severini,E A Phillips,J C Wang,J R Patterson,S Z Li,S Stone,K Zhang,P U E Onyisi,D H Miller,J Li,A Tomaradze,J Butt,Y Kubota

doi:10.1103/physrevlett.95.102003

Abstract

The h_c(1P1) state of charmonium has been observed in the reaction \psi(2S) -> \pi0 h_c -> (\gamma\gamma)(\gamma\eta_c) using 3.08 million \psi(2S) decays recorded in the CLEO detector. Data have been analyzed both for the inclusive reaction, where the decay products of the \eta_c are not identified, and for exclusive reactions, in which \eta_c decays are reconstructed in seven hadronic decay channels. We find M(h_c)=3524.4 +/- 0.6 +/- 0.4 MeV which corresponds to a hyperfine splitting \Delta M_{hf}(1P) \equiv <M(3PJ)>-M(1P1)=+1.0+/-0.6+/-0.4 MeV, and B(\psi(2S)->\pi0 h_c)xB(h_c->\gamma\eta_c)=(4. +/-0.8+/-0.7)x10^{-4}.

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