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ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2007, vol. 98, p. -

Observation of B decays to two kaons

Lin S. W., Chang P., Abe K., Abe K., Adachi I., Aihara H., Anipko D., Arinstein K., Aulchenko V., Aushev T., Aziz T., Bakich A. M., Barberio E., Bay A., Bedny I., Belous K., Bitenc U., Bizjak I., Blyth S., Bondar A., Bozek A., Bračko M., Chao Y., Chen A., Chen K. F., Chen W. T., Cheon B. G., Chistov R., Choi S. K., Choi Y., Choi Y. K., Dalseno J., Dash M., Dragic J., Eidelman S., Fratina S., Gabyshev N., Gershon T., Go A., Gokhroo G., Golob B., Ha H., Haba J., Hara T., Hayasaka K., Hayashii H., Hazumi M., Heffernan D., Hoshi Y., Hou S., Hou W. S., Hsiung Y. B., Iijima T., Ikado K., Imoto A., Inami K., Ishikawa A., Ishino H., Itoh R., Iwasaki M., Iwasaki Y., Kaji H., Kang J. H., Katayama N., Kawai H., Kawasaki T., Khan H. R., Kichimi H., Kim Y. J., Kinoshita K., Korpar S., Križan P., Kulasiri R., Kuo C. C., Kwon Y. J., Lange J. S., Lee J., Lee M. J., Lee S. E., Lesiak T., Limosani A., Mandl F., Matsumoto T., McOnie S., Mitaroff W., Miyabayashi K., Miyake H., Miyata H., Miyazaki Y., Mizuk R., Mohapatra D., Mori T., Nakamura I., Nakano E.

Using 449×106 BB̄ pairs collected with the Belle detector at the KEKB asymmetric-energy e+e- collider, we observe clear signals for B+→K̄0K+ and B0→K̄0K0 decays with 5.3σ and 6.0σ significance, respectively. We measure the branching fractions B(B+→K̄0K+)=(1.22-0.28-0.16+0.32+0.13)×10-6 and B(B0→K̄0K0)=(0.87-0.20+0.25±0.09)×10-6, and partial-rate asymmetries ACP(B+→K̄0K+)=0.13-0.24+0.23±0.02 and ACP(B0→K̄0K0)=-0.58-0.66+0.73±0.04. From a simultaneous fit, we also obtain B(B+→K0π+)=(22.8-0.7+0.8±1.3)×10-6 and ACP(B+→K0π+)=0.03±0.03±0.01. The first and second error in the branching fractions and the partial-rate asymmetries are statistical and systematic, respectively. No signal is observed for B0→K+K- decays, and for this branching fraction, we set an upper limit of 4.1×10-7 at the 90% confidence level. © 2007 The American Physical Society.