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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2005, vol. 71, p. 1-8

Measurement of the B̄<sup>0</sup> → D *<sup>+</sup>ℓ<sup>-</sup>ν̄<inf>ℓ</inf> decay rate and |V<inf>cb</inf>|

Aubert B., Barate R., Boutigny D., Couderc F., Gaillard J. M., Hicheur A., Karyotakis Y., Lees J. P., Tisserand V., Zghiche A., Palano A., Pompili A., Chen J. C., Qi N. D., Rong G., Wang P., Zhu Y. S., Eigen G., Ofte I., Stugu B., Abrams G. S., Borgland A. W., Breon A. B., Brown D. N., Button-Shafer J., Cahn R. N., Charles E., Day C. T., Gill M. S., Gritsan A. V., Groysman Y., Jacobsen R. G., Kadel R. W., Kadyk J., Kerth L. T., Kolomensky Yu G., Kukartsev G., Lynch G., Mir L. M., Oddone P. J., Orimoto T. J., Pripstein M., Roe N. A., Ronan M. T., Shelkov V. G., Wenzel W. A., Barrett M., Ford K. E., Harrison T. J., Hart A. J., Hawkes C. M., Morgan S. E., Watson A. T., Fritsch M., Goetzen K., Held T., Koch H., Lewandowski B., Pelizaeus M., Steinke M., Boyd J. T., Chevalier N., Cottingham W. N., Kelly M. P., Latham T. E., Wilson F. F., Cuhadar-Donszelmann T., Hearty C., Knecht N. S., Mattison T. S., McKenna J. A., Thiessen D., Khan A., Kyberd P., Teodorescu L., Blinov V. E., Druzhinin V. P., Golubev V. B., Ivanchenko V. N., Kravchenko E. A., Onuchin A. P., Serednyakov S. I., Skovpen Yu I., Solodov E. P., Yushkov A. N., Best D., Bruinsma M., Chao M., Eschrich I., Kirkby D., Lankford A. J., Mandelkern M., Mommsen R. K., Roethel W., Stoker D. P., Buchanan C., Hartfiel B. L., Foulkes S. D., Gary J. W., Shen B. C.

We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V<inf>cb</inf>| based on a sample of about 53 700 B̄<sup>0</sup> → D*<sup>+</sup>ℓ<sup>-</sup>ν̄<inf>ℓ</inf> decays observed by the BABAR detector. We obtain the branching fraction averaged over ℓ = e, μ, B(B̄<sup>0</sup> → D*<sup>+</sup>ℓ <sup>-</sup>ν̄<inf>ℓ</inf>) = (4.90 ± 0.07(stat.) <inf>-0.35</inf><sup>+0.36</sup>(syst.))%. We measure the differential decay rate as a function of w, the relativistic boost γ of the D*<sup>+</sup> in the B̄<sup>0</sup> rest frame. By extrapolating dΓ/dw to the kinematic limit w → 1, we extract the product of |V <inf>cb</inf>| and the axial form factor A<inf>1</inf>(w = 1). We combine this measurement with a lattice QCD calculation of A<inf>1</inf>(w = 1) to determine |V<inf>cb</inf>) = (38.7 ± 0.3(stat.) ± 1.7(syst.) <inf>-1.3</inf><sup>+1.5</sup>(theory)) × 10<sup>-3</sup>. © 2005 The American Physical Society.