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ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2013, vol. 110, p. -

Study of e+e-→π+π-J/ψ and observation of a charged charmoniumlike state at Belle

Liu Z. Q., Shen C. P., Yuan C. Z., Adachi I., Aihara H., Asner D. M., Aulchenko V., Aushev T., Aziz T., Bakich A. M., Bala A., Belous K., Bhardwaj V., Bhuyan B., Bischofberger M., Bondar A., Bonvicini G., Bozek A., Bračko M., Brodzicka J., Browder T. E., Chang P., Chekelian V., Chen A., Chen P., Cheon B. G., Chistov R., Cho K., Chobanova V., Choi S. K., Choi Y., Cinabro D., Dalseno J., Danilov M., Doležal Z., Drásal Z., Drutskoy A., Dutta D., Dutta K., Eidelman S., Epifanov D., Farhat H., Fast J. E., Feindt M., Ferber T., Frey A., Gaur V., Gabyshev N., Ganguly S., Gillard R., Goh Y. M., Golob B., Haba J., Hayasaka K., Hayashii H., Horii Y., Hoshi Y., Hou W. S., Hsiung Y. B., Hyun H. J., Iijima T., Inami K., Ishikawa A., Itoh R., Iwasaki Y., Joffe D., Julius T., Kah D. H., Kang J. H., Kawasaki T., Kiesling C., Kim H. J., Kim J. B., Kim J. H., Kim K. T., Kim M. J., Kim Y. J., Kinoshita K., Klucar J., Ko B. R., Kodyš P., Korpar S., Križan P., Krokovny P., Kuhr T., Kwon Y. J., Lange J. S., Lee S. H., Li J., Li Y., Libby J., Liu C.

The cross section for e+e -→π+π-J/ψ between 3.8 and 5.5 GeV is measured with a 967 fb-1 data sample collected by the Belle detector at or near the Υ(nS) (n=1,2,...,5) resonances. The Y(4260) state is observed, and its resonance parameters are determined. In addition, an excess of π+π-J/ψ production around 4 GeV is observed. This feature can be described by a Breit-Wigner parametrization with properties that are consistent with the Y(4008) state that was previously reported by Belle. In a study of Y(4260)→π+π-J/ψ decays, a structure is observed in the M(π±J/ψ) mass spectrum with 5.2σ significance, with mass M=(3894.5±6.6±4. 5) MeV/c2 and width Γ=(63±24±26) MeV/c2, where the errors are statistical and systematic, respectively. This structure can be interpreted as a new charged charmoniumlike state. © 2013 American Physical Society.