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ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2006, vol. 97, p. -

Study of J/ψ→pp̄,ΛΛ̄ and observation of ηc→ΛΛ̄ at Belle

Wu C. H., Wang M. Z., Abe K., Adachi I., Aihara H., Aulchenko V., Aushev T., Bahinipati S., Bakich A. M., Balagura V., Bay A., Belous K., Bitenc U., Bizjak I., Blyth S., Bondar A., Bozek A., Browder T. E., Chao Y., Chen A., Chen W. T., Cheon B. G., Choi Y., Choi Y. K., Chuvikov A., Cole S., Dalseno J., Danilov M., Dash M., Eidelman S., Gabyshev N., Gershon T., Go A., Gokhroo G., Gorišek A., Ha H., Haba J., Hayasaka K., Hayashii H., Hazumi M., Heffernan D., Hokuue T., Hou S., Hou W. S., Hsiung Y. B., Iijima T., Inami K., Ishikawa A., Itoh R., Iwasaki M., Iwasaki Y., Kang J. H., Kataoka S. U., Katayama N., Kawai H., Kawasaki T., Khan H. R., Kichimi H., Kim H. J., Kim H. O., Kim Y. J., Križan P., Krokovny P., Kulasiri R., Kumar R., Kuo C. C., Kuzmin A., Kwon Y. J., Leder G., Lee J., Lee Y. J., Lesiak T., Lin S. W., Liventsev D., Majumder G., Mandl F., Matsumoto T., Matyja A., McOnie S., Mitaroff W., Miyabayashi K., Miyake H., Miyata H., Miyazaki Y., Mizuk R., Mori T., Nakano E., Nakao M., Natkaniec Z., Nishida S., Nitoh O., Ogawa S., Ohshima T., Okabe T., Okuno S., Olsen S. L., Onuki Y., Ozaki H., Pakhlov P.

We study the baryonic charmonium decays of B mesons B+→ηcK+ and B+→J/ψK+, where the ηc and J/ψ subsequently decay into a pp̄ or ΛΛ̄ pair. We measure the J/ψ→pp̄ and ΛΛ̄ anisotropy parameters αB=-0.60±0. 13±0.14 (pp̄), -0.44±0.51±0.31 (ΛΛ̄ ) and compare to results from e+e-→J/ψ formation experiments. We also report the first observation of ηc→ΛΛ̄. The measured branching fraction is B(ηc→ΛΛ̄)=(0.87-0.21+0. 24(stat)-0.14+0.09(syst)±0.27(PDG))×10-3. This study is based on a 357fb-1 data sample recorded on the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. © 2006 The American Physical Society.