Sumitted to PubDB: 2024-01-10

Category: Proceeding, Visibility: Public

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Authors	Henrik Junkerkalefeld
Date	2023-12-29
Belle II Number	BELLE2-CONF-PROC-2023-049
Abstract	We present recent tests of lepton universality as crucial probes of the Standard Model in semileptonic $B$-meson decays at Belle II. All presented analyses use a data sample collected at the $\mathrm{{\rm Y}}(4S)$ resonance by the Belle II experiment corresponding to an integrated luminosity of $189{\mathrm{fb}}^{-1}$. We report three analyses that probe light-lepton universality: The first measurement of a complete set of five angular asymmetries using ${\overline{B}}^0\to D^{\ast +}{\ell }^{-}{\overline{\nu }}_{\ell }$ decays, followed by a measurement of the forward-backward asymmetry in untagged ${\overline{B}}^0\to D^{\ast +}{\ell }^{-}{\overline{\nu }}_{\ell }$ decays, and finally, measurements of the branching-fraction ratios $R(D_{e/\mu }^{\ast +})=\mathcal{B}({\overline{B}}^0\to D^{\ast +}{e}^{-}{\overline{\nu }}_e)/\mathcal{B}({\overline{B}}^0\to D^{\ast +}{\mu }^{-}{\overline{\nu }}_{\mu })$, using the same untagged data set, along with the first measurement of the inclusive light-lepton ratio $R(X_{e/\mu })=\mathcal{B}(\overline{B}\to X{e}^{-}{\overline{\nu }}_e)/\mathcal{B}(\overline{B}\to X{\mu }^{-}{\overline{\nu }}_{\mu })$. Furthermore, we present two tests of heavy-to-light lepton universality. In the first test, we report the measurement of the branching-fraction ratio $R(D_{\tau /\ell }^{\ast })$ using hadronic tagging. In the second test, we present the first measurement of the inclusive ratio $R(X_{\tau /\ell })$. All presented results are consistent with their corresponding Standard Model predictions and, where applicable, with the experimental world averages.

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  latest upload: 2024-12-02