Measurement of the CKM matrix element |<i>V<sub>cb</sub></i>| from <i>B</i><SUP>0</SUP> → <i>D</i>*<i><SUP>-</SUP>l</i><SUP>+</SUP>ν<sub><i>l</i></sub> at Belle

Abstract

We present a new measurement of the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V-cb vertical bar from B-0 -> D*(-)l(+)nu(l) decays, reconstructed with the full Belle data set of 711 fb(-1) integrated luminosity. Two form factor parametrizations, originally conceived by the Caprivi-Lellouch-Neubert (CLN) and the Boyd, Grinstein and Lebed (BGL) groups, are used to extract the product F(1)eta(EW)vertical bar V-cb vertical bar and the decay form factors, where F(1) is the normalization factor and eta(EW) is a small electroweak correction. In the CLN parametrization we find F(1)eta(EW)vertical bar V-cb vertical bar = (35.06 +/- 0.15 +/- 0.56) x 10(-3), rho(2) = 1.106 +/- 0.031 +/- 0.007, R-1 (1) = 1.229 +/- 0.028 +/- 0.009, R-2(1) = 0.852 +/- 0.021 +/- 0.006. For the BGL parametrization we obtain ,F(1)eta(EW)vertical bar V-cb vertical bar = (34.93 +/- 0.23 +/- 0.59) x 10(-3), which is consistent with the world average when correcting for F(1)eta(EW). The branching fraction of B-0 -> D*(-)l(+)nu(l )is measured to be B(B-0 -> D*(-)l(+)nu(l))= (4.90 +/- 0.02 +/- 0.16)%. We also present a new test of lepton flavor universality violation in semileptonic B decays, B(B-0 -> D*(-)e(+)nu)/B(B-0 -> D*(-)mu(+)nu) = 1.01 +/- 0.01 +/- 0.03. The errors quoted correspond to the statistical and systematic uncertainties, respectively. This is the most precise measurement of F(1)eta(EW)vertical bar V-cb vertical bar and form factors to date and the first experimental study of the BGL form factor parametrization in an experimental measurement.