Determination of the form factors for the decay B-0 -> D*(-)l(+)nu(l) and of the CKM matrix element vertical bar Vcb vertical bar
mag(2008)
摘要
We present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V-cb vertical bar and of the parameters rho(2), R-1(1), and R-2(1), which fully characterize the form factors for the B-0 -\u003e D*(-)center dot(+)nu(center dot) decay in the framework of heavy-quark effective field theory. The results, based on a selected sample of about 52 800 B-0 -\u003e D*(-)center dot(+)nu(center dot) decays, recorded by the BABAR detector, are rho(2)=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)vertical bar V-cb vertical bar=(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, rho(2)=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)vertical bar V-cb vertical bar=(34.4 +/- 0.3 +/- 1.1)x10(-3). Using lattice calculations for the axial form factor F(1), we extract vertical bar V-cb vertical bar=(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)%.
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