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arXiv · 1204.0246

Evidence for the Direct Two-Photon Transition from $ψ(3686)$ to $J/ψ$

BESIII Collaboration·M. Ablikim·M. N. Achasov·D. J. Ambrose·F. F. An·Q. An·Z. H. An·J. Z. Bai·R. B. Ferroli·Y. Ban·J. Becker·N. Berger·M. B. Bertani·J. M. Bian·E. Boger·O. Bondarenko·I. Boyko·R. A. Briere·V. Bytev·X. Cai·A. C. Calcaterra·G. F. Cao·J. F. Chang·G. Chelkov·G. Chen·H. S. Chen·J. C. Chen·M. L. Chen·S. J. Chen·Y. Chen·Y. B. Chen·H. P. Cheng·Y. P. Chu·D. Cronin-Hennessy·H. L. Dai·J. P. Dai·D. Dedovich·Z. Y. Deng·A. Denig·I. Denysenko·M. Destefanis·W. M. Ding·Y. Ding·L. Y. Dong·M. Y. Dong·S. X. Du·J. Fang·S. S. Fang·L. Fava·F. Feldbauer·C. Q. Feng·C. D. Fu·J. L. Fu·Y. Gao·C. Geng·K. Goetzen·W. X. Gong·W. Gradl·M. Greco·M. H. Gu·Y. T. Gu·Y. H. Guan·A. Q. Guo·L. B. Guo·Y. P. Guo·Y. L. Han·X. Q. Hao·F. A. Harris·K. L. He·M. He·Z. Y. He·T. Held·Y. K. Heng·Z. L. Hou·H. M. Hu·J. F. Hu·T. Hu·B. Huang·G. M. Huang·J. S. Huang·X. T. Huang·Y. P. Huang·T. Hussain·C. S. Ji·Q. Ji·X. B. Ji·X. L. Ji·L. K. Jia·L. L. Jiang·X. S. Jiang·J. B. Jiao·Z. Jiao·D. P. Jin·S. Jin·F. F. Jing·N. Kalantar-Nayestanaki·M. Kavatsyuk·W. Kuehn·W. Lai·J. S. Lange
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Abstract

The two-photon transition $ψ(3686)\toγγJ/ψ$ is studied in a sample of 106 million $ψ(3686)$ decays collected by the BESIII detector. The branching fraction is measured to be $(3.1\pm0.6(\unit{stat})^{+0.8}_{-1.0}(\unit{syst})) \times10^{-4}$ using $J/ψ\to e^+e^-$ and $J/ψ\toμ^+μ^-$ decays, and its upper limit is estimated to be $4.5\times10^{-4}$ at the 90% conference level. This work represents the first measurement of a two-photon transition among charmonium states. The orientation of the $ψ(3686)$ decay plane and the $J/ψ$ polarization in this decay are also studied. In addition, the product branching fractions of sequential $E1$ transitions $ψ(3686)\toγχ_{cJ}, χ_{cJ}\toγJ/ψ(J=0,1,2)$ are reported.

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BESIII Collaboration, M. Ablikim, M. N. Achasov, D. J. Ambrose, F. F. An, Q. An, Z. H. An, J. Z. Bai, R. B. Ferroli, Y. Ban, J. Becker, N. Berger, M. B. Bertani, J. M. Bian, E. Boger, O. Bondarenko, I. Boyko, R. A. Briere, V. Bytev, X. Cai, A. C. Calcaterra, G. F. Cao, J. F. Chang, G. Chelkov, G. Chen, H. S. Chen, J. C. Chen, M. L. Chen, S. J. Chen, Y. Chen, Y. B. Chen, H. P. Cheng, Y. P. Chu, D. Cronin-Hennessy, H. L. Dai, J. P. Dai, D. Dedovich, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, W. M. Ding, Y. Ding, L. Y. Dong, M. Y. Dong, S. X. Du, J. Fang, S. S. Fang, L. Fava, F. Feldbauer, C. Q. Feng, C. D. Fu, J. L. Fu, Y. Gao, C. Geng, K. Goetzen, W. X. Gong, W. Gradl, M. Greco, M. H. Gu, Y. T. Gu, Y. H. Guan, A. Q. Guo, L. B. Guo, Y. P. Guo, Y. L. Han, X. Q. Hao, F. A. Harris, K. L. He, M. He, Z. Y. He, T. Held, Y. K. Heng, Z. L. Hou, H. M. Hu, J. F. Hu, T. Hu, B. Huang, G. M. Huang, J. S. Huang, X. T. Huang, Y. P. Huang, T. Hussain, C. S. Ji, Q. Ji, X. B. Ji, X. L. Ji, L. K. Jia, L. L. Jiang, X. S. Jiang, J. B. Jiao, Z. Jiao, D. P. Jin, S. Jin, F. F. Jing, N. Kalantar-Nayestanaki, M. Kavatsyuk, W. Kuehn, W. Lai, J. S. Lange. 2012-11-01. Evidence for the Direct Two-Photon Transition from $ψ(3686)$ to $J/ψ$. https://doi.org/10.1103/physrevlett.109.172002

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