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ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2006, vol. 96, p. -

Observation of b→dγ and determination of |Vtd/Vts|

Mohapatra D., Nakao M., Nishida S., Abe K., Abe K., Adachi I., Aihara H., Anipko D., Arinstein K., Asano Y., Aulchenko V., Aushev T., Bahinipati S., Bakich A. M., Balagura V., Barbero M., Bedny I., Bitenc U., Bizjak I., Blyth S., Bondar A., Bozek A., Bračko M., Browder T. E., Chao Y., Chen A., Chen K. F., Chen W. T., Cheon B. G., Chistov R., Choi Y., Chuvikov A., Cole S., Dalseno J., Danilov M., Dash M., Dragic J., Drutskoy A., Eidelman S., Epifanov D., Fratina S., Gabyshev N., Gershon T., Gokhroo G., Golob B., Gorišek A., Ha H. C., Haba J., Hara T., Hastings N. C., Hayasaka K., Hayashii H., Hazumi M., Hinz L., Hokuue T., Hoshi Y., Hou S., Hou W. S., Hsiung Y. B., Iijima T., Imoto A., Inami K., Ishikawa A., Ishino H., Itoh R., Iwasaki M., Iwasaki Y., Kang J. H., Kataoka S. U., Katayama N., Kawasaki T., Khan H. R., Kichimi H., Kim H. J., Kim H. O., Kim S. M., Kinoshita K., Korpar S., Križan P., Krokovny P., Kulasiri R., Kumar R., Kuo C. C., Kuzmin A., Kwon Y. J., Lange J. S., Leder G., Lee J., Lesiak T., Limosani A., Lin S. W., Liventsev D., Majumder G., Mandl F., Marlow D.

We report the observation of the flavor-changing neutral current process b→dγ using a sample of 386×106 B meson pairs accumulated by the Belle detector at the KEKB e+e- collider. We measure branching fractions for the exclusive modes B-→ρ-γ, B̄0→ρ0γ, and B̄0→ωγ. Assuming that these three modes are related by isospin, we find B(B̄→(ρ,ω)γ)=(1.32-0.31+0.34(stat)-0.09+0.10(syst)) ×10-6 with a significance of 5.1σ. This result is used to determine the ratio of Cabibbo-Kobayashi-Maskawa matrix elements |Vtd/Vts| to be 0.199-0.025+0.026(exp)-0.015+0.018(theor). © 2006 The American Physical Society.