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ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2014, vol. 112, p. -

Observation of e + e - → γ X (3872) at BESIII

Ablikim M., Achasov M. N., Ai X. C., Albayrak O., Ambrose D. J., An F. F., An Q., Bai J. Z., Baldini Ferroli R., Ban Y., Bennett J. V., Bertani M., Bian J. M., Boger E., Bondarenko O., Boyko I., Braun S., 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 J. C., Chen M. L., Chen S. J., Chen X., Chen X. R., Chen Y. B., Cheng H. P., Chu X. K., 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 C., Dong J., Dong L. Y., Dong M. Y., Du S. X., Fan J. Z., Fang J., Fang S. S., Fang Y., Fava L., Feng C. Q., Fu C. D., Fu J. L., Fuks O., Gao Q., 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 T., Guo Y. P., Han Y. L., Harris F. A., He K. L., He M., He Z. Y., Held T., Heng Y. K., Hou Z. L., Hu C., Hu H. M., Hu J. F., Hu T., Huang G. M., Huang G. S., Huang J. S., Huang L., Huang X. T., Huang Y., Hussain T., Ji C. S., Ji Q., Ji Q. P.

With data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.009 to 4.420 GeV, the process e+e-→γX(3872) is observed for the first time with a statistical significance of 6.3σ. The measured mass of the X(3872) is (3871.9±0.7stat±0.2syst) MeV/c2, in agreement with previous measurements. Measurements of the product of the cross section σ[e+e-→γX(3872)] and the branching fraction B[X(3872)→π+π-J/ψ] at center-of-mass energies 4.009, 4.229, 4.260, and 4.360 GeV are reported. Our measurements are consistent with expectations for the radiative transition process Y(4260)→γX(3872). © 2014 American Physical Society.