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ISSN - 03702693, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2015, vol. 749, p. 414-420

An improved limit for Γ<inf>ee</inf> of X(3872) and Γ<inf>ee</inf> measurement of ψ(3686)

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., Bondarenko O., Boyko I., Briere R. A., Cai H., Cai X., Cakir O., Calcaterra A., Cao G. F., Cetin S. A., Chang J. F., Chelkov G., Chen G., Chen H. S., Chen H. Y., Chen J. C., Chen M. L., Chen S. J., Chen X., Chen X. R., Chen Y. B., Cheng H. P., Chu X. K., Cibinetto G., Cronin-Hennessy D., Dai H. L., Dai J. P., Dbeyssi A., Dedovich D., Deng Z. Y., Denig A., Denysenko I., Destefanis M., De Mori F., Ding Y., Dong C., Dong J., Dong L. Y., Dong M. Y., Du S. X., Duan P. F., Fan J. Z., Fang J., Fang S. S., Fang X., Fang Y., Fava L., Feldbauer F., Felici G., Feng C. Q., Fioravanti E., Fritsch M., Fu C. D., Gao Q., Gao X. Y., Gao Y., Gao Z., Garzia I., 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., Guo Y. P.

© 2015 The Authors. Using the data sets taken at center-of-mass energies above 4 GeV by the BESIII detector at the BEPCII storage ring, we search for the reaction e<sup>+</sup>e<sup>-</sup>→γ<inf>ISR</inf>X(3872)→γ<inf>ISR</inf>π<sup>+</sup>π<sup>-</sup>J/ψ via the Initial State Radiation technique. The production of a resonance with quantum numbers J<sup>PC</sup>=1<sup>++</sup> such as the X(3872) via single photon e<sup>+</sup>e<sup>-</sup> annihilation is forbidden, but is allowed by a next-to-leading order box diagram. We do not observe a significant signal of X(3872), and therefore give an upper limit for the electronic width times the branching fraction Γ<inf>ee</inf><sup>X(3872)</sup>B(X(3872)→π<sup>+</sup>π<sup>-</sup>J/ψ)<0.13 eV at the 90% confidence level. This measurement improves upon existing limits by a factor of 46. Using the same final state, we also measure the electronic width of the ψ(3686) to be Γ<inf>ee</inf><sup>ψ(3686)</sup>=2213±18<inf>stat</inf>±99<inf>sys</inf> eV.