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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2013, vol. 88, p. -

Observation of a structure at 1.84 GeV/c2 in the 3(π+π -) mass spectrum in J/ψ→γ3(π+π -) decays

Ablikim M., Achasov M. N., Albayrak O., Ambrose D. J., An F. F., An Q., Bai J. Z., Baldini Ferroli R., Ban Y., Becker J., Bennett J. V., Bertani M., Bian J. M., Boger E., Bondarenko O., Boyko I., Briere R. A., Bytev V., 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 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., Feng C. Q., Friedel P., Fu C. D., Fu J. L., Fuks O., 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., Ji X. B., Ji X. L., Jiang L. L., Jiang X. S., Jiao J. B.

With a sample of 225.3×106 J/ψ events taken with the BESIII detector, the decay J/ψ→γ3(π+π-) is analyzed. A structure at 1.84 GeV/c2 is observed in the 3(π+π -) invariant mass spectrum with a statistical significance of 7.6σ. The mass and width are measured to be M=1842.2±4.2-2.6+7.1 MeV/c2 and Γ=83±14±11 MeV. The product branching fraction is determined to be B(J/ψ→γX(1840))×B(X(1840) →3(π+π-))=(2.44±0.36-0.74+0.60) ×10-5. No η′ signals are observed in the 3(π+π-) invariant mass spectrum, and the upper limit of the branching fraction for the decay η′→3(π +π-) is set to be 3.1×10-5 at a 90% confidence level. © 2013 American Physical Society.