Evidence for B semileptonic decays into the charmed baryon Λ

We present the first evidence for B semileptonic decays into the charmed baryon Λc based on 420 fb−1 of data collected at the Υ (4S) resonance with the BABAR detector at the PEP-II e+e− storage rings. Events are tagged by fully reconstructing one of the B mesons in a hadronic decay mode. We measure the relative branching fraction B(B → Λc Xlνl)/B(B → Λc /Λ − c X) = (3.2 ± 0.9stat. ± 0.9syst.)%. The significance of the signal including the systematic uncertainty is 4.9 standard deviations. Submitted to the 34th International Conference on High-Energy Physics, ICHEP 08, 29 July—5 August 2008, Philadelphia, Pennsylvania. Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309 Work supported in part by Department of Energy contract DE-AC03-76SF00515. November 2008 The BABAR Collaboration, B. Aubert, M. Bona, Y. Karyotakis, J. P. Lees, V. Poireau, E. Prencipe, X. Prudent, V. Tisserand Laboratoire de Physique des Particules, IN2P3/CNRS et Université de Savoie, F-74941 Annecy-Le-Vieux, France J. Garra Tico, E. Grauges Universitat de Barcelona, Facultat de Fisica, Departament ECM, E-08028 Barcelona, Spain L. Lopez, A. Palano, M. Pappagallo INFN Sezione di Bari; Dipartmento di Fisica, Università di Bari, I-70126 Bari, Italy G. Eigen, B. Stugu, L. Sun University of Bergen, Institute of Physics, N-5007 Bergen, Norway G. S. Abrams, M. Battaglia, D. N. Brown, R. N. Cahn, R. G. Jacobsen, L. T. Kerth, Yu. G. Kolomensky, G. Lynch, I. L. Osipenkov, M. T. Ronan, K. Tackmann, T. Tanabe Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720, USA C. M. Hawkes, N. Soni, A. T. Watson University of Birmingham, Birmingham, B15 2TT, United Kingdom H. Koch, T. Schroeder Ruhr Universität Bochum, Institut für Experimentalphysik 1, D-44780 Bochum, Germany D. Walker University of Bristol, Bristol BS8 1TL, United Kingdom D. J. Asgeirsson, B. G. Fulsom, C. Hearty, T. S. Mattison, J. A. McKenna University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1 M. Barrett, A. Khan Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom V. E. Blinov, A. D. Bukin, A. R. Buzykaev, V. P. Druzhinin, V. B. Golubev, A. P. Onuchin, S. I. Serednyakov, Yu. I. Skovpen, E. P. Solodov, K. Yu. Todyshev Budker Institute of Nuclear Physics, Novosibirsk 630090, Russia M. Bondioli, S. Curry, I. Eschrich, D. Kirkby, A. J. Lankford, P. Lund, M. Mandelkern, E. C. Martin, D. P. Stoker University of California at Irvine, Irvine, California 92697, USA S. Abachi, C. Buchanan University of California at Los Angeles, Los Angeles, California 90024, USA J. W. Gary, F. Liu, O. Long, B. C. Shen, G. M. Vitug, Z. Yasin, L. Zhang University of California at Riverside, Riverside, California 92521, USA Deceased