# Determination of the Form Factors for the Decay $B^0 \to D^{*-} l^+ \nu_l$ and of the CKM Matrix Element $|V_{cb}|$

Abstract : We present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V_{cb}| and of the parameters rho^2, R_1(1), and R_2(1), which fully characterize the form factors for the B0 -> D*- l+ nu_l decay in the framework of heavy-quark effective theory. The results, based on a selected sample of about 52,800 B0 -> D*- l+ nu_l decays, recorded by the BaBar detector, are rho2=1.157+-0.094+-0.027, R_1(1)=1.327+-0.131+-0.043, R_2(1)=0.859+-0.077+-0.021, and F(1)|V_cb|=(34.7+-0.4+-1.0)x10^-3. The first error is the statistical and the second is the systematic uncertainty. Combining these measurements with the previous BaBar measurement of the form factors, which employs a different fit technique on a partial sample of the data, we improve the statistical precision of the result, rho2=1.191+-0.048+-0.028, R_1(1)=1.429+-0.061+-0.044, R_2(1)=0.827+-0.038+-0.022, and F(1)|V_cb| = (34.4+-0.3+-1.1)x10^-3. Using lattice calculations for the axial form factor $\mathcal{F}(1)$, we extract |V_cb| =(37.4+-0.3+-1.2+1.2-1.4)x10^-3, where the third error is due to the uncertainty in F(1). We also present a measurement of the exclusive branching fraction, B = (4.69+-0.04+-0.34)%.
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-00262461
Contributor : Claudine Bombar <>
Submitted on : Tuesday, March 11, 2008 - 5:41:04 PM
Last modification on : Wednesday, September 16, 2020 - 4:20:01 PM

### Citation

B. Aubert, M. Bona, D. Boutigny, Y. Karyotakis, J.P. Lees, et al.. Determination of the Form Factors for the Decay $B^0 \to D^{*-} l^+ \nu_l$ and of the CKM Matrix Element $|V_{cb}|$. Physical Review D, American Physical Society, 2008, 77, pp.032002. ⟨10.1103/PhysRevD.77.032002⟩. ⟨in2p3-00262461⟩

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