Measurement of higher-order multipole amplitudes in ψ (3686) →γχc1,2 with χc1,2 →γJ /ψ and search for the transition ηc (2S) →γJ /ψ

M. Ablikim, M. N. Achasov, X. C. Ai, O. Albayrak, M. Albrecht, D. J. Ambrose, A. Amoroso, F. F. An, Q. An, J. Z. Bai, R. Baldini Ferroli, Y. Ban, D. W. Bennett, J. V. Bennett, M. Bertani, D. Bettoni, J. M. Bian, F. Bianchi, E. Boger, I. BoykoR. A. Briere, H. Cai, X. Cai, O. Cakir, A. Calcaterra, G. F. Cao, S. A. Cetin, J. F. Chang, G. Chelkov, G. Chen, H. S. Chen, H. Y. Chen, J. C. Chen, M. L. Chen, S. Chen, S. J. Chen, X. Chen, X. R. Chen, Y. B. Chen, H. P. Cheng, X. K. Chu, G. Cibinetto, H. L. Dai, J. P. Dai, A. Dbeyssi, D. Dedovich, Z. Y. Deng, A. Denig, H. Muramatsu, R. Poling, (BESIII Collaboration)

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Using 106 ×106 ψ(3686) events collected with the BESIII detector, we measure multipole amplitudes for the decay ψ(3686)→γχc1,2→γγJ/ψ beyond the dominant electric-dipole amplitudes. The normalized magnetic-quadrupole (M2) amplitude for ψ(3686)→γχc1,2→γγJ/ψ and the normalized electric-octupole amplitudes for ψ(3686)→γχc2, χc2→γJ/ψ are determined. The M2 amplitudes for ψ(3686)→γχc1 and χc1,2→γJ/ψ are found to differ significantly from zero and are consistent with theoretical predictions. We also obtain the ratios of M2 contributions of ψ(3686) and J/ψ decays to χc1,2, b21/b22=1.35±0.72 and a21/a22=0.617±0.083, which agree well with theoretical expectations. By considering the multipole contributions of χc1,2, we measure the product branching fractions for the cascade decays ψ(3686)→γχc0,1,2→γγJ/ψ and search for the process ηc(2S)→γJ/ψ through ψ(3686)→γηc(2S). The product branching fraction for ψ(3686)→γχc0→γγJ/ψ is 3σ larger than published measurements, while those of ψ(3686)→γχc1,2→γγJ/ψ are consistent. No significant signal for the decay ψ(3686)→γηc(2S)→γγJ/ψ is observed, and the upper limit of the product branching fraction at the 90% confidence level is determined.

Original languageEnglish (US)
Article number072004
JournalPhysical Review D
Issue number7
StatePublished - Apr 1 2017

Bibliographical note

Funding Information:
This work is supported in part by National Key Basic Research Program of China under Contract No. 2015CB856700; National Natural Science Foundation of China (NSFC) under Contracts No. 11125525, No. 11235011, No. 11322544, No. 11335008, No. 11425524, No. 11475187, No. 11521505, and No. 11575198; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; the CAS Center for Excellence in Particle Physics; the Collaborative Innovation Center for Particles and Interactions; Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contracts No. 11179007, No. U1232201, and No. U1332201; CAS under Contracts No. KJCX2-YW-N29 and No. KJCX2-YW-N45; 100 Talents Program of CAS; National 1000 Talents Program of China; Institute of Nuclear and Particle Physics (INPAC) and Shanghai Key Laboratory for Particle Physics and Cosmology; German Research Foundation under Collaborative Research Center Contract No. CRC-1044; Istituto Nazionale di Fisica Nucleare, Italy; Koninklijke Nederlandse Akademie van Wetenschappen under Contract No. 530-4CDP03; Ministry of Development of Turkey under Contract No. DPT2006K-120470; NSFC under Contracts No. 11405046 and No. U1332103; Russian Foundation for Basic Research under Contract No. 14-07-91152; The Swedish Research Council; U.S. Department of Energy under Contracts No. DE-FG02-04ER41291, No. DE-FG02-05ER41374, No. DE-SC0012069, No. DESC0010118; U.S. National Science Foundation; University of Groningen and the Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt; and World-Class University (WCU) Program of National Research Foundation of Korea under Contract No. R32-2008-000-10155-0.

Publisher Copyright:
© 2017 American Physical Society.

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