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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2009, vol. 79, p. -

Measurement of the semileptonic decays B̄→Dτ-ν̄τ and B̄→D*τ-ν̄τ

Aubert B., Bona M., Karyotakis Y., Lees J. P., Poireau V., Prencipe E., Prudent X., Tisserand V., Tico J. Garra, Grauges E., Lopez L., Palano A., Pappagallo M., Eigen G., Stugu B., Sun L., Abrams G. S., Battaglia M., Brown D. N., Jacobsen R. G., Kerth L. T., Kolomensky Yu G., Lynch G., Osipenkov I. L., Ronan M. T., Tackmann K., Tanabe T., Hawkes C. M., Soni N., Watson A. T., Koch H., Schroeder T., Asgeirsson D. J., Fulsom B. G., Hearty C., Mattison T. S., McKenna J. A., Barrett M., Khan A., Blinov V. E., Bukin A. D., Buzykaev A. R., Druzhinin V. P., Golubev V. B., Onuchin A. P., Serednyakov S. I., Skovpen Yu I., Solodov E. P., Todyshev K. Yu, Bondioli M., Curry S., Eschrich I., Kirkby D., Lankford A. J., Lund P., Mandelkern M., Martin E. C., Stoker D. P., Abachi S., Buchanan C., Atmacan H., Gary J. W., Liu F., Long O., Vitug G. M., Yasin Z., Zhang L., Sharma V., Campagnari C., Hong T. M., Kovalskyi D., Mazur M. A., Richman J. D., Beck T. W., Eisner A. M., Flacco C. J., Heusch C. A., Kroseberg J., Lockman W. S., Martinez A. J., Schalk T., Schumm B. A., Seiden A., Wilson M. G., Winstrom L. O., Cheng C. H., Doll D. A., Echenard B., Fang F., Hitlin D. G., Narsky I., Piatenko T., Porter F. C., Andreassen R., Mancinelli G., Meadows B. T., Mishra K.

We present measurements of the semileptonic decays B-→D0τ- ν̄τ, B-→D*0τ-ν̄τ, B̄0→D+τ- ν̄τ, and B̄0→D*+τ-ν̄τ, which are sensitive to non-standard model amplitudes in certain scenarios. The data sample consists of 232×106Υ(4S)→BB̄ decays collected with the BABAR detector at the PEP-II e+e- collider. We select events with a D or D* meson and a light lepton (=e or μ) recoiling against a fully reconstructed B meson. We perform a fit to the joint distribution of lepton momentum and missing mass squared to distinguish signal B̄→D(*) τ-ν̄τ(τ-→-ν̄ντ) events from the backgrounds, predominantly B̄→D(*)-ν̄. We measure the branching-fraction ratios R(D)B(B̄→Dτ-ν̄τ)/ B(B̄→D-ν̄) and R(D*)B(B̄→D*τ- ν̄τ)/B(B̄→D*-ν̄) and, from a combined fit to B- and B̄0 channels, obtain the results R(D)=(41.6±11.7±5.2) % and R(D*)=(29.7±5.6±1.8)%, where the uncertainties are statistical and systematic. Normalizing to measured B-→D(*)0- ν̄ branching fractions, we obtain B(B̄→Dτ-ν̄τ) =(0.86±0.24±0.11±0.06)% and B(B̄→D*τ- ν̄τ)=(1.62±0.31±0.10±0.05)%, where the additional third uncertainty is from the normalization mode. We also present, for the first time, distributions of the lepton momentum, |p*|, and the squared momentum transfer, q2. © 2009 The American Physical Society.