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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2013, vol. 88, p. -

Study of exclusive B→Xuℓν decays and extraction of |Vub| using full reconstruction tagging at the Belle experiment

Sibidanov A., Varvell K. E., Adachi I., Aihara H., Asner D. M., Aulchenko V., Aushev T., Bakich A. M., Bala A., Bozek A., Bračko M., Browder T. E., Chekelian V., Chen P., Cheon B. G., Chilikin K., Chistov R., Cho I. S., Cho K., Chobanova V., Choi Y., Cinabro D., Dalseno J., Danilov M., Dingfelder J., Doležal Z., Drásal Z., Drutskoy A., Dutta D., Eidelman S., Epifanov D., Farhat H., Fast J. E., Ferber T., Frey A., Gaur V., Ganguly S., Gillard R., Goh Y. M., Golob B., Haba J., Hayashii H., Hoshi Y., Hou W. S., Hyun H. J., Iijima T., Ishikawa A., Itoh R., Iwasaki Y., Julius T., Kah D. H., Kang J. H., Kawasaki T., Kiesling C., Kim D. Y., Kim H. J., Kim J. B., Kim J. H., Kim K. T., Kim Y. J., Klucar J., Ko B. R., Kodyš P., Korpar S., Križan P., Krokovny P., Kronenbitter B., Kuhr T., Kuzmin A., Kwon Y. J., Lee S. H., Li J., Li Y., Libby J., Liu Y., Liventsev D., Lukin P., Matvienko D., Miyabayashi K., Miyata H., Mohanty G. B., Moll A., Mussa R., Nagasaka Y., Nakano E., Nakao M., Natkaniec Z., Nayak M., Nedelkovska E., Ng C., Nisar N. K.

We report the results of a study of the exclusive semileptonic decays B-→π0ℓ-ν̄ℓ, B ̄0→π+ℓ -ν̄ℓ, B-→ρ0ℓ -ν̄ℓ, B̄0→ρ +ℓ-ν̄ℓ and B -→ωℓ-ν̄ℓ, where ℓ represents an electron or a muon. The events are tagged by fully reconstructing a second B meson in the event in a hadronic decay mode. The measured branching fractions are B(B-→π0ℓ -ν̄ℓ)=(0.80±0.08±0.04) ×10-4, B(B̄0→π+ℓ -ν̄ℓ)=(1.49±0.09±0.07) ×10-4, B(B-→ρ0ℓ -ν̄ℓ)=(1.83±0.10±0.10) ×10-4, B(B̄0→ρ+ℓ -ν̄ℓ)=(3.22±0.27±0.24) ×10-4, and B(B-→ωℓ -ν̄ℓ)=(1.07±0.16±0.07) ×10-4, where the first error is statistical and the second one is systematic. The obtained branching fractions are inclusive of soft photon emission. We also determine the branching fractions as a function of the 4-momentum transfer squared to the leptonic system q2=(pℓ+p ν)2, where pℓ and pν are the lepton and neutrino 4-momenta, respectively. Using the pion modes, a recent light cone sum rule calculation, lattice QCD results and a model-independent description of the hadronic form factor, a value of the Cabibbo-Kobayashi- Maskawa matrix element |Vub|=(3.52±0.29)×10-3 is extracted. A structure in the two-pion invariant mass distribution near 1.3 GeV/c2, which might be dominated by the decay B-→f 2(1270)ℓ-ν̄ℓ, f 2→π+π-, is seen. These results are obtained from a 711 fb-1 data sample that contains 772×106 BB̄ pairs, collected near the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. © 2013 American Physical Society.