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ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2008, vol. 100, p. -

Observation of anomalous Υ(1S)π+π- and Υ(2S)π+π- Production near the Υ(5S) resonance

Chen K. F., Hou W. S., Shapkin M., Sokolov A., Adachi I., Aihara H., Arinstein K., Aulchenko V., Aushev T., Bakich A. M., Balagura V., Bay A., Belous K., Bhardwaj V., Bitenc U., Bondar A., Bozek A., Bračko M., Brodzicka J., Browder T. E., Chang P., Chao Y., Chen A., Chen W. T., Chistov R., Choi Y., Dalseno J., Danilov M., Dash M., Drutskoy A., Eidelman S., Gabyshev N., Golob B., Ha H., Haba J., Hayasaka K., Hayashii H., Hazumi M., Heffernan D., Hoshi Y., Hsiung Y. B., Hyun H. J., Iijima T., Inami K., Ishikawa A., Ishino H., Itoh R., Iwasaki M., Iwasaki Y., Kah D. H., Kang J. H., Kapusta P., Katayama N., Kawai H., Kawasaki T., Kichimi H., Kim H. O., Kim S. K., Kim Y. J., Kinoshita K., Korpar S., Križan P., Krokovny P., Kumar R., Kuo C. C., Kwon Y. J., Lange J. S., Lee J. S., Lee M. J., Lesiak T., Limosani A., Lin S. W., Liu Y., Liventsev D., Mandl F., McOnie S., Medvedeva T., Mitaroff W., Miyabayashi K., Miyake H., Miyata H., Miyazaki Y., Mizuk R., Moloney G. R., Nakao M., Natkaniec Z., Nishida S., Nitoh O., Ogawa S., Ohshima T., Okuno S., Olsen S. L., Ostrowicz W., Ozaki H.

We report the first observation of e+e-→Υ(1S)π+π-, Υ(2S)π+π-, and first evidence for e+e-→Υ(3S)π+π-, Υ(1S)K+K-, near the peak of the Υ(5S) resonance at s∼10.87GeV. The results are based on a data sample of 21.7fb-1 collected with the Belle detector at the KEKB e+e- collider. Attributing the signals to the Υ(5S) resonance, the partial widths Γ(Υ(5S)→Υ(1S)π+π-)=0. 59±0.04(stat)±0.09(syst)MeV and Γ(Υ(5S)→Υ(2S) π+π-)=0.85±0.07(stat)±0.16(syst)MeV are obtained from the observed cross sections. These values exceed by more than 2 orders of magnitude the previously measured partial widths for dipion transitions between lower Υ resonances. © 2008 The American Physical Society.