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ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2008, vol. 101, p. -

Observation of a near-threshold enhancement in the e+e- →Λc+Λc- Cross section using initial-state radiation

Pakhlova G., Adachi I., Aihara H., Arinstein K., Aulchenko V., Aushev T., Bakich A. M., Balagura V., Bedny I., Bhardwaj V., Bitenc U., Bondar A., Bozek A., Bračko M., Brodzicka J., Browder T. E., Chang P., Chen A., Cheon B. G., Chiang C. C., Chistov R., Cho I. S., Choi S. K., Choi Y., Dalseno J., Danilov M., Dash M., Eidelman S., Gabyshev N., Ha H., Haba J., Hayasaka K., Hazumi M., Heffernan D., Hoshi Y., Hou W. S., 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., Katayama N., Kawai H., Kawasaki T., Kichimi H., Kim H. J., Kim H. O., Kim S. K., Kim Y. I., Kim Y. J., Kinoshita K., Križan P., Krokovny P., Kumar R., Kuzmin A., Kwon Y. J., Kyeong S. H., Lange J. S., Lee J. S., Lee S. E., Lesiak T., Li J., Limosani A., Liu C., Liventsev D., Mandl F., Matyja A., Miyabayashi K., Miyata H., Miyazaki Y., Mizuk R., Mori T., Nakano E., Nakao M., Natkaniec Z., Nishida S., Nitoh O., Noguchi S., Ogawa S., Ohshima T., Okuno S., Olsen S. L., Ozaki H., Pakhlov P., Palka H., Park C. W., Park H.

We report a measurement of the exclusive e+e-→Λc+Λc- cross section as a function of center-of-mass energy near the Λc+Λc- threshold. A clear peak with a significance of 8.2σ is observed in the Λc+Λc- invariant mass distribution just above threshold. With an assumption of a resonance origin for the observed peak, a mass and width of M=[4634-7+8(stat)-8+5(syst)]MeV/c2 and Γtot=[92- 24+40(stat)-21+10(syst)]MeV are determined. The analysis is based on a study of events with initial-state-radiation photons in a data sample collected with the Belle detector at the Υ(4S) resonance and nearby continuum with an integrated luminosity of 695fb-1 at the KEKB asymmetric-energy e+e- collider. © 2008 The American Physical Society.