Tests of Light-Lepton Universality in Angular Asymmetries of B0 →d∗-ℓν Decays

We present the first comprehensive tests of the universality of the light leptons in the angular distributions of semileptonic B0-meson decays to charged spin-1 charmed mesons. We measure five angular-asymmetry observables as functions of the decay recoil that are sensitive to lepton-universality-violating contributions. We use events where one neutral B is fully reconstructed in (4S)→BB¯ decays in data corresponding to 189 fb-1 integrated luminosity from electron-positron collisions collected with the Belle II detector. We find no significant deviation from the standard model expectations.