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We present a new measurement of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| from B0 → D*-vℓ decays, reconstructed with the full Belle data set of 711 fb−1 integrated luminosity. Two form factor parametrizations, originally conceived by the Caprini-Lellouch-Neubert (CLN) and the Boyd, Grinstein and Lebed (BGL) groups, are used to extract the product F(1)ηEW||Vcb| and the decay form factors, where F(1) is the normalization factor and ηEW is a small electroweak correction. In the CLN parametrization we find F(1)ηEW||Vcb|=(35.06 ± 0.15 ± 0.56) × 10−3, ρ2 =1.106 ± 0.031± 0.007, R1(1) ¼ 1.229 ± 0.028 ± 0.009, R2(1) = 0.852 ± 0.021 ± 0.006. For the BGL parametrization we obtain F(1)ηEW|Vcb|=(34.93 ± 0.23 ± 0.59) × 10−3, which is consistent with the world average when correcting for F(1) ηEW. The branching fraction of B0 → D−lþνl is measured to be B(B0 → D−lþνlÞ¼ð4.90 0.02 0.16Þ%. We also present a new test of lepton flavor universality violation in semileptonic B decays, BðB0→D−eþνÞ BðB0→D−μþνÞ ¼ 1.01 0.01 0.03. The errors quoted correspond to the statistical and systematic uncertainties, respectively. This is the most precise measurement of Fð1ÞηEWjVcbj and form factors to date and the first experimental study of the BGL form factor parametrization in an experimental measurement.

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Waheed, E., Urquijo, P., Ferlewicz, D., Adachi, I., Adamczyk, K., Aihara, H., Al Said, S., Asner, D. M., Atmacan, H., Aushev, T., Ayad, R., Babu, V., Badhrees, I., Bansal, V., Behera, P., Beleño, C., Bernlochner, F., Bhuyan, B., Bilka, T., … Zhukova, V. (2019). Measurement of the CKM matrix element . Physical Review D, 100(5).

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