Measurement of |Vcb | using ¯ B 0 → D ∗+ ℓ − ¯νℓ Decays The BABAR Collaboration

A preliminary measurement of |Vcb| and the branching fraction B(B̄0 → Dlν̄l) has been performed based on a sample of about 55,700 B̄0 → Dlν̄l decays recorded with the BABAR detector. The decays are identified in the D∗+ → D0π+ final state, with the D0 reconstructed in three different decay modes. The differential decay rate is measured as a function of the relativistic boost of the D∗+ in the B̄0 rest frame. The value of the differential decay rate at ‘zero recoil’, namely the point at which the D∗+ is at rest in the B̄0 frame, is predicted in Heavy Quark Effective Theory as a kinematic factor times F(1)|Vcb|, where F is the unique form factor governing the decay. We extrapolate the measured differential decay rate to the zero recoil point and obtain F(1)|Vcb| = (34.03 ± 0.24± 1.31) × 10−3. Using a theoretical calculation for F(1) we extract |Vcb| = (37.27 ± 0.26(stat.) ± 1.43(syst.) −1.2(theo.))× 10. From the integrated decay rate we obtain B(B̄0 → Dlν̄l) = (4.68 ± 0.03 ± 0.29)%. Contributed to the XXIst International Symposium on Lepton and Photon Interactions at High Energies, 8/11 — 8/16/2003, Fermilab, Illinois USA This work is dedicated to the memory of Paolo Poropat. Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309 Work supported in part by Department of Energy contract DE-AC03-76SF00515. The BABAR Collaboration, B. Aubert, R. Barate, D. Boutigny, J.-M. Gaillard, A. Hicheur, Y. Karyotakis, J. P. Lees, P. Robbe, V. Tisserand, A. Zghiche Laboratoire de Physique des Particules, F-74941 Annecy-le-Vieux, France A. Palano, A. Pompili Università di Bari, Dipartimento di Fisica and INFN, I-70126 Bari, Italy J. C. Chen, N. D. Qi, G. Rong, P. Wang, Y. S. Zhu Institute of High Energy Physics, Beijing 100039, China G. Eigen, I. Ofte, B. Stugu University of Bergen, Inst. of Physics, N-5007 Bergen, Norway G. S. Abrams, A. W. Borgland, A. B. Breon, D. N. Brown, J. Button-Shafer, R. N. Cahn, E. Charles, C. T. Day, M. S. Gill, A. V. Gritsan, Y. Groysman, R. G. Jacobsen, R. W. Kadel, J. Kadyk, L. T. Kerth, Yu. G. Kolomensky, J. F. Kral, G. Kukartsev, C. LeClerc, M. E. Levi, G. Lynch, L. M. Mir, P. J. Oddone, T. J. Orimoto, M. Pripstein, N. A. Roe, A. Romosan, M. T. Ronan, V. G. Shelkov, A. V. Telnov, W. A. Wenzel Lawrence Berkeley National Laboratory and University of California, Berkeley, CA 94720, USA K. Ford, T. J. Harrison, C. M. Hawkes, D. J. Knowles, S. E. Morgan, R. C. Penny, A. T. Watson, N. K. Watson University of Birmingham, Birmingham, B15 2TT, United Kingdom T. Held, K. Goetzen, H. Koch, B. Lewandowski, M. Pelizaeus, K. Peters, H. Schmuecker, M. Steinke Ruhr Universität Bochum, Institut für Experimentalphysik 1, D-44780 Bochum, Germany N. R. Barlow, J. T. Boyd, N. Chevalier, W. N. Cottingham, M. P. Kelly, T. E. Latham, C. Mackay, F. F. Wilson University of Bristol, Bristol BS8 1TL, United Kingdom K. Abe, T. Cuhadar-Donszelmann, C. Hearty, T. S. Mattison, J. A. McKenna, D. Thiessen University of British Columbia, Vancouver, BC, Canada V6T 1Z1 P. Kyberd, A. K. McKemey Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom V. E. Blinov, A. D. Bukin, V. B. Golubev, V. N. Ivanchenko, E. A. Kravchenko, A. P. Onuchin, S. I. Serednyakov, Yu. I. Skovpen, E. P. Solodov, A. N. Yushkov Budker Institute of Nuclear Physics, Novosibirsk 630090, Russia D. Best, M. Bruinsma, M. Chao, D. Kirkby, A. J. Lankford, M. Mandelkern, R. K. Mommsen, W. Roethel, D. P. Stoker University of California at Irvine, Irvine, CA 92697, USA C. Buchanan, B. L. Hartfiel University of California at Los Angeles, Los Angeles, CA 90024, USA