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ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2005, vol. 95, p. -

Observation of B+→pΛ̄γ

Lee Y. J., Wang M. Z., Abe K., Abe K., Aihara H., Asano Y., Aulchenko V., Aushev T., Bahinipati S., Bakich A. M., Bedny I., Bitenc U., Bizjak I., Bondar A., Bozek A., Bračko M., Brodzicka J., Browder T. E., Chang M. C., Chang P., Chao Y., Chen A., Chen K. F., Chen W. T., Cheon B. G., Chistov R., Choi S. K., Chuvikov A., Cole S., Dalseno J., Danilov M., Dash M., Drutskoy A., Eidelman S., Enari Y., Fang F., Fratina S., Gabyshev N., Garmash A., Gershon T., Gokhroo G., Golob B., Gorišek A., Haba J., Hayasaka K., Hazumi M., Hinz L., Hokuue T., Hoshi Y., Hou S., Hou W. S., Hsiung Y. B., Iijima T., Imoto A., Inami K., Ishikawa A., Itoh R., Iwasaki M., Iwasaki Y., Kang J. H., Kang J. S., Kapusta P., Katayama N., Kawai H., Kawasaki T., Khan H. R., Kichimi H., Kim H. J., Kim S. K., Kim S. M., Kinoshita K., Korpar S., Križan P., Krokovny P., Kumar S., Kuo C. C., Kuzmin A., Kwon Y. J., Leder G., Lee S. E., Lesiak T., Li J., Lin S. W., Liventsev D., Mandl F., Matsumoto T., Matyja A., Mitaroff W., Miyake H., Miyata H., Mizuk R., Moloney G. R., Nagamine T., Nagasaka Y., Nakano E.

We report the first observation of the radiative hyperonic B decay B+→pΛ̄γ, using a 140fb-1 data sample recorded on the Υ(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider. The measured branching fraction is B(B+→pΛ̄γ)= (2.16-0.53+0.58±0.20)×10-6. We examine its MpΛ̄ distribution and observe a peak near threshold. This feature is expected by the short-distance b→sγ transition. A search for B+→pΣ̄ 0γ yields no significant signal, and we set a 90% confidence-level upper limit on the branching fraction of B(B+→pΣ̄0γ)<4. 6×10-6. © 2005 The American Physical Society.