EPJ

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EPJ C - Particles and Fields
Particles and Fields
Eur. Phys. J. C 9, 43-53
DOI 10.1007/s100529901104

Heavy-heavy form factors and generalized factorization

M. Ciuchini1 - R. Contino2 - E. Franco2 - G. Martinelli2

1 Dipartimento di Fisica, Università di Roma Tre and INFN, Sezione di Roma III, Via della Vasca Navale 84, I-00146 Rome, Italy
2 Dipartimento di Fisica, Università ``La Sapienza" and INFN, Sezione di Roma, P.le A. Moro 2, I-00185 Rome, Italy

Received: 7 October 1998 / Revised version: 4 December 1998 / Published online: 20 May 1999

Abstract
We reanalyze $B\to D\pi$ and $B \to K J/\psi$ data to extract a set of parameters which give the relevant hadronic matrix elements in terms of factorized amplitudes. Various sources of theoretical uncertainties are studied, in particular those depending on the model adopted for the form factors. We find that the fit to the $B\to D\pi$ branching ratios substantially depends on the model describing the Isgur-Wise function and on the value of its slope. This dependence can be reduced by substituting the $BR(B\to D\pi)$ with suitable ratios of non-leptonic to differential semileptonic BRs. In this way, we obtain a model-independent determination of these parameters. Using these results, the $B\to D$ form factors at $q^2=M_\pi^2$ can be extracted from a fit of the $BR(B\to D\pi)$.The comparison between the form factors obtained in this way and the corresponding measurements in semileptonic decays can be used as a test of (generalized) factorization free from the uncertainties due to heavy-heavy form factor modeling. Finally, we present predictions for as-yet-unmeasured $D\pi$ and DK branching ratios and extract fDs and fDs* from $B\to DD_s$ decays. We find $f_{D_s}=270\pm 45$ MeV and $f_{D_s^*}=260\pm 40$ MeV, in good agreement with recent measurements and lattice calculations.

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