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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Abstract

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
Volume95
Issue number7
DOIs
StatePublished - Apr 1 2017

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    Ablikim, M., Achasov, M. N., Ai, X. C., Albayrak, O., Albrecht, M., Ambrose, D. J., Amoroso, A., An, F. F., An, Q., Bai, J. Z., Baldini Ferroli, R., Ban, Y., Bennett, D. W., Bennett, J. V., Bertani, M., Bettoni, D., Bian, J. M., Bianchi, F., Boger, E., ... (BESIII Collaboration) (2017). 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. Physical Review D, 95(7), [072004]. https://doi.org/10.1103/PhysRevD.95.072004