Ablikim, M.Achasov, M. N.Ai, X. C.Albayrak, O.Albrecht, M.Ambrose, D. J.Amoroso, A.Lou, XinchouBESIII Collaboration2017-03-312017-03-312015-08-072015-08-070370-2693http://hdl.handle.net/10735.1/5331Using 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⁺e⁻→ γ(ISR}X(3872) → γ{ISR}π⁺π⁻J/ψ via the Initial State Radiation technique. The production of a resonance with quantum numbers JPC=1⁺⁺ such as the X(3872) via single photon e+e- 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{ee} ^{X(3872)} ℬ(X(3872) → π⁺π⁻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 {ee} ^{ψ(3686)} = 2213 ± 18{stat} ± 99{sys} eV. © 2015 The Authors.enCC BY 4.0 (Attribution)©2015 The Authorshttp://creativecommons.org/licenses/by/4.0/CharmoniumX(3872) mesonsΨ(3686) mesonsAtomic spectroscopyElectron-positron interactionsBranching fractions (Nuclear physics)Particles (Nuclear physics)—CharmArticleAblikim, M., M. N. Achasov, X. C. Ai, O. Albayrak, et al. 2015. "An improved limit for Γ_{ee} of X(3872) and Γ_{ee} measurement of ψ(3686)." Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 749, doi: 10.1016/j.physletb.2015.08.013749