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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2012, vol. 86, p. -

Evidence for B -→Ds+K -ℓ -ν ̄ℓ and search for B -→Ds*+K -ℓ -ν ̄ℓ

Stypula J., Rozanska M., Adachi I., Adamczyk K., Aihara H., Asner D. M., Aushev T., Bakich A. M., Bhardwaj V., Bhuyan B., Bischofberger M., Bondar A., Bonvicini G., Bozek A., Bračko M., Browder T. E., Chang M. C., Chang P., Chekelian V., Chen A., Chen P., Cheon B. G., Chistov R., Cho I. S., Cho K., Choi Y., Dalseno J., Danilov M., Dingfelder J., Doleal Z., Drásal Z., Drutskoy A., Eidelman S., Farhat H., Fast J. E., Gaur V., Gabyshev N., Gillard R., Goh Y. M., Golob B., 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., Julius T., Kang J. H., Kapusta P., Kawasaki T., Kichimi H., Kiesling C., Kim H. J., Kim J. B., Kim J. H., Kim K. T., Kim Y. J., Kinoshita K., Ko B. R., Kody P., Korpar S., Kouzes R. T., Krian P., Krokovny P., Kuhr T., Kumita T., Kuzmin A., Kwon Y. J., Lee S. H., Li J., Li Y., Libby J., Liu C., Liu Y., Liu Z. Q., Liventsev D., Louvot R., Miyabayashi K., Miyata H., Miyazaki Y., Mizuk R., Mohanty G. B., Moll A., Muramatsu N., Nakano E.

We report measurements of the decays B -→Ds(*)+K -ℓ -ν ̄ℓ in a data sample containing 657×106BB̄ pairs collected with the Belle detector at the KEKB asymmetric-energy e +e - collider. We observe a signal with a significance of 6σ for the combined D s and Ds* modes and find the first evidence of the B -→Ds+K -ℓ -ν ̄ℓ decay with a significance of 3.4σ. We measure the following branching fractions: B(B -→Ds+K -ℓ -ν ̄ℓ)=(0.30±0.09(stat)-0.08+0.11(syst)) ×10 -3 and B(B -→Ds(*)+K -ℓ -ν ̄ℓ)=(0.59±0.12(stat) ±0.15(syst))×10 -3 and set an upper limit B(B -→Ds*+K -ℓ -ν ̄ℓ)<0.56×10 -3 at the 90% confidence level. We also present the first measurement of the Ds+K - invariant mass distribution in these decays, which is dominated by a prominent peak around 2.6GeV/c2. © 2012 American Physical Society.