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ISSN - 03702693, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2007, vol. 648, p. 139-148

Measurements of branching fractions and q2 distributions for B → π ℓ ν and B → ρ ℓ ν decays with B → D(*) ℓ ν decay tagging

Hokuue T., Abe K., Abe K., Adachi I., Aihara H., Asano Y., Aushev T., Bakich A. M., Balagura V., Barberio E., Barbero M., Bay A., Bedny I., Belous K., Bitenc U., Bizjak I., Blyth S., Bondar A., Bozek A., Bračko M., Browder T. E., Chang P., Chen A., Chen W. T., Choi Y., Chuvikov A., Cole S., Dalseno J., Danilov M., Dash M., Drutskoy A., Eidelman S., Gabyshev N., Garmash A., Gershon T., Gokhroo G., Gorišek A., Ha H., Haba J., Hara K., Hara T., Hayasaka K., Hayashii H., Hazumi M., Hinz L., Hoshi Y., Hou S., Hou W. S., Iijima T., Ikado K., Imoto A., Inami K., Ishikawa A., Itoh R., Iwasaki M., Iwasaki Y., Kakuno H., Kang J. H., Kapusta P., Kataoka S. U., Kawai H., Kawasaki T., Khan H. R., Kim H. J., Kim H. O., Kinoshita K., Kozakai Y., Križan P., Krokovny P., Kulasiri R., Kumar R., Kuo C. C., Kuzmin A., Kwon Y. J., Lee J., Lesiak T., Li J., Limosani A., Lin S. W., Majumder G., Mandl F., Matsumoto T., Matyja A., McOnie S., Mitaroff W., Miyake H., Miyata H., Miyazaki Y., Mohapatra D., Nakamura I., Nakano E., Natkaniec Z., Nishida S., Nitoh O., Nozaki T., Ogawa S., Ohshima T.

We report measurements of the charmless semileptonic decays B0 → π- / ρ- ℓ+ ν and B+ → π0 / ρ0 ℓ+ ν, based on a sample of 2.75 × 108B over(B, ̄) events collected at the Υ{hooked} (4 S) resonance with the Belle detector at the KEKB e+ e- asymmetric collider. In this analysis, the accompanying B meson is reconstructed in the semileptonic mode B → D(*) ℓ ν, enabling detection of the signal modes with high purity. We measure the branching fractions B (B0 → π- ℓ+ ν) = (1.38 ± 0.19 ± 0.14 ± 0.03) × 10-4, B (B0 → ρ- ℓ+ ν) = (2.17 ± 0.54 ± 0.31 ± 0.08) × 10-4, B (B+ → π0 ℓ+ ν) = (0.77 ± 0.14 ± 0.08 ± 0.00) × 10-4 and B (B+ → ρ0 ℓ+ ν) = (1.33 ± 0.23 ± 0.17 ± 0.05) × 10-4, where the errors are statistical, experimental systematic, and systematic due to form factor uncertainties, respectively. For each mode we also present the partial branching fractions in three q2 intervals: q2 < 8, 8 ≤ q2 < 16, and q2 ≥ 16   GeV2 / c2. From our partial branching fractions for B → π ℓ ν and recent results for the form factor from unquenched Lattice QCD calculations, we obtain values of the CKM matrix element | Vu b |. © 2007 Elsevier B.V. All rights reserved.