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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2011, vol. 84, p. -

First observation of radiative B0→·K0γ decays and measurements of their time-dependent CP violation

Sahoo H., Browder T. E., Adachi I., Asner D. M., Aulchenko V., Bakich A. M., Barberio E., Belous K., Bhardwaj V., Bhuyan B., Bondar A., Bozek A., Bračko M., Brovchenko O., Chen A., Chen P., Cheon B. G., Cho K., Choi Y., Dalseno J., Doleal Z., Drásal Z., Eidelman S., Epifanov D., Fast J. E., Gaur V., Gabyshev N., Haba J., Hayasaka K., Hayashii H., Horii Y., Hoshi Y., Hou W. S., Hsiung Y. B., Hyun H. J., Iijima T., Inami K., Ishikawa A., Itoh R., Iwabuchi M., Iwasaki Y., Iwashita T., Joshi N. J., Julius T., Kang J. H., Kawasaki T., Kiesling C., Kim H. J., Kim H. O., Kim J. B., Kim J. H., Kim K. T., Kim M. J., Kim S. K., Kim Y. J., Kinoshita K., Ko B. R., Kobayashi N., Koblitz S., Kody P., Korpar S., Krian P., Kuhr T., Kumar R., Kumita T., Kuzmin A., Kwon Y. J., Lange J. S., Lee M. J., Lee S. H., Li J., Li Y., Libby J., Lim C. L., Liu Z. Q., Liventsev D., Louvot R., Matvienko D., McOnie S., Miyabayashi K., Miyata H., Miyazaki Y., Mizuk R., Mohanty G. B., Mori T., Nakao M., Natkaniec Z., Ng C.

We report the first observation of the radiative decay B0→· K0γ using a data sample of 772×106 BB̄ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We observe a signal of 37±8 events with a significance of 5.4 standard deviations including systematic uncertainties. The measured branching fraction is B(B0→·K0γ)= (2.74±0.60±0.32)×10-6, where the uncertainties are statistical and systematic, respectively. We also report the first measurements of time-dependent CP-violation parameters: S ·KS0γ=+0.74-1.05+0.72(stat)-0.24+0.10(syst) and A ·KS0γ=+0.35±0.58(stat)-0.10+0.23(syst). Furthermore, we measure B(B+→·K+γ)=(2. 48±0.30±0.24)×10-6, ACP=-0. 03±0.11±0.08, and find that the signal is concentrated in the M·K mass region near threshold. © 2011 American Physical Society.