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ISSN - 16741137, Chinese Physics C, 2010, vol. 34, p. 421-426

Observation of a pp̄ mass threshold enhancement in Ψ′ π+π- J/Ψ(J/Ψ γ p) decay

Ablikim M., Achasov M. N., An L., An Q., An Z. H., Bai J. Z., Ban Y., Berger N., Bian J. M., Boyko I., Briere R. A., Bytev V., Cai X., Cao G. F., Cao X. X., Chang J. F., Chelkov G., Chen G., Chen H. S., Chen J. C., Chen L. P., Chen M. L., Chen P., Chen S. J., ChenY.B. , Chu Y. P., Cronin-Hennessy D., Dai H. L., Dai J. P., Dedovich D., Deng Z. Y., Denysenko I., Destefanis M., Ding Y., Dong L. Y., Dong M. Y., Du S. X., Duan M. Y., Fang J., Feng C. Q., Fu C. D., Fu J. L., Gao Y., Geng C., Goetzen K., Gong W. X., Greco M., Grishin S., Gu Y. T., Guo A. Q., Guo L. B., Guo Y. P., Han S. Q., Harris F. A., He K. L., He M., He Z. Y., Heng Y. K., Hou Z. L., Hu H. M., Hu J. F., Hu T., Hu X. W., Huang B., Huang G. M., Huang J. S., Huang X. T., Huang Y. P., Ji C. S., Ji Q., Ji X. B., Ji X. L., Jia L. K., Jiang L. L., Jiang X. S., Jiao J. B., Jin D. P., Jin S., Komamiya S., Kuehn W., Lange S., Leung J. K C, Li C., Li C., Li D. M., Li F., Li G., Li H. B., Li J., Li J. C., Li L., Li L., Li Q. J., Li W. D., Li W. G., Li X. L., Li X. N., Li X. Q., Li X. R.

The decay channel Ψ′ π+π- J/Ψ(J/Ψ γp) is studied using a sample of 1.06 × 10 8 Ψ′ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the p invariant mass spectrum. The enhancement can be fitted with an S-wave Breit-Wigner resonance function with a resulting peak mass of M 1861+6 -13 (stat) +7 -26 (syst) MeV/c2 and a narrow width that is Γ < 38 MeV/c2 at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with well established mesons. © 2010 Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.