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Determination of the form factors for the decay B0→D*-l+νl and of the CKM matrix element


We present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| and of the parameters ρ2, R1(1), and R2(1), which fully characterize the form factors for the B0→D*- +ν decay in the framework of heavy-quark effective field theory. The results, based on a selected sample of about 52800 B0→D*- +ν decays, recorded by the BABAR detector, are ρ2=1.157±0.094±0.027, R1(1)=1. 327±0.131±0.043, R2(1)=0.859±0.077±0.021, and F(1)|Vcb|=(34.7±0.4±1.0)×10-3. 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, ρ2=1.191±0.048±0.028, R1(1)=1.429±0.061±0.044, R2(1)=0.827±0.038±0.022, and F(1)|Vcb|=(34.4±0.3±1.1)×10-3. Using lattice calculations for the axial form factor F(1), we extract |Vcb|=(37.4±0. 3±1.2±1.41.2)×10-3, 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)%. © 2008 The American Physical Society.

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