We determine the Cabibbo-Kobayashi-Maskawa matrix-element magnitude |Vcb| using ̄B0→D*+l− ̄νl decays reconstructed in 189 fb−1 of collision data collected by the Belle II experiment, located at the SuperKEKB e+e− collider. Partial decay rates are reported as functions of the recoil parameter w and three decay angles separately for electron and muon final states. We obtain |Vcb| using the Boyd-Grinstein-Lebed and Caprini-Lellouch-Neubert parametrizations, and find |Vcb|BGL=(40.57±0.31±0.95±0.58)×10−3 and |Vcb|CLN=(40.13±0.27±0.93±0.58)×10−3 with the uncertainties denoting statistical components, systematic components, and components from the lattice QCD input, respectively. The branching fraction is measured to be B( ̄B0→D*+l− ̄νl)=(4.922±0.023±0.220)%. The ratio of branching fractions for electron and muon final states is found to be 0.998±0.009±0.020. In addition, we determine the forward-backward angular asymmetry and the D*+ longitudinal polarization fractions. All results are compatible with lepton-flavor universality in the Standard Model.
