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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2010, vol. 82, p. -

Evidence for B-→τ-ν̄τ with a semileptonic tagging method

Hara K., Iijima T., Aihara H., Aulchenko V., Aushev T., Aziz T., Bakich A. M., Barberio E., Belous K., Bischofberger M., Bondar A., Bozek A., Bračko M., Browder T. E., Chang P., Chao Y., Chen A., Cheon B. G., Chiang C. C., Cho I. S., Choi Y., Dalseno J., Danilov M., Doležal Z., Dungel W., Eidelman S., Gabyshev N., Goldenzweig P., Golob B., Ha H., Hasegawa Y., Hayasaka K., Hayashii H., Horii Y., Hoshi Y., Hsiung Y. B., Hyun H. J., Inami K., Iwabuchi M., Iwasaki Y., Julius T., Kang J. H., Kawai H., Kawasaki T., Kichimi H., Kiesling C., Kim H. J., Kim H. O., Kim J. H., Kim M. J., Kim Y. J., Kinoshita K., Ko B. R., Kodyž P., Korpar S., Kreps M., Križan P., Krokovny P., Kuhr T., Kumita T., Kuzmin A., Kwon Y. J., Kyeong S. H., Lee M. J., Lee S. H., Li J., Limosani A., Liu Y., Liventsev D., Louvot R., Matyja A., McOnie S., Miyabayashi K., Miyata H., Miyazaki Y., Mohanty G. B., Mori T., Nakano E., Nakao M., Nakazawa H., Neubauer S., Nishida S., Nishimura K., Nitoh O., Nozaki T., Ogawa S., Ohshima T., Okuno S., Olsen S. L.

We present a measurement of the decay B-→τ -ν̄τ using a data sample containing 657×106 BB̄ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. A sample of B+B- pairs are tagged by reconstructing one B+ meson decaying semileptonically. We detect the B-→τ -ν̄τ candidate in the recoil. We obtain a signal with a significance of 3.6 standard deviations including systematic uncertainties, and measure the branching fraction to be B(B-→τ -ν̄τ)=[1.54-0.37+0.38(stat)-0.31+0.29(syst)] ×10-4. This result confirms the evidence for B -→τ-ν̄τ obtained in a previous Belle measurement that used a hadronic B tagging method. © 2010 The American Physical Society.