Measurement of Angular Coefficients of B ¯ → D ℓ ν ¯ ℓ : Implications for | V c b | and Tests of Lepton Flavor Universality

We measure the complete set of angular coefficients J i for exclusive B ¯ → D * ℓ ν ¯ ℓ decays ( ℓ = e , μ ). Our analysis uses the full 711 fb − 1 Belle dataset with hadronic tag-side reconstruction. The results allow us to extract the form factors describing the B ¯ → D * transition and the Cabibbo-Kobayashi-Maskawa matrix element | V cb | . Using recent lattice QCD calculations for the hadronic form factors, we find | V cb | = ( 40.7 ± 0.7 ) × 10 − 3 using the Boyd-Grinstein-Lebed parametrization, compatible with determinations from inclusive semileptonic decays. We search for lepton flavor universality violation as a function of the hadronic recoil parameter w and investigate the differences of the electron and muon angular distributions. We find no deviation from standard model expectations.