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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2013, vol. 87, p. -

Evidence for η<inf>c</inf>→γγ and measurement of J/ψ→3γ

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

© 2013 American Physical Society. The decay of J/ψ to three photons is studied using ψ(3686) →π<sup>+</sup>π<sup>-</sup>J/ψ in a sample of 1.0641×108 ψ(3686) events collected with the BESIII detector. Evidence of the direct decay of η<inf>c</inf> to two photons, η<inf>c</inf>→γγ , is reported, and the product branching fraction is determined to be B(J/ψ→γη<inf>c</inf>,η<inf>c</inf>→γγ)= (4.5±1.2±0.6)×10<sup>-</sup>6, where the first error is statistical and the second is systematic. The branching fraction for J/ψ→3γ is measured to be (11.3±1.8±2.0) ×10<sup>-</sup>6 with improved precision.