PoS - Proceedings of Science
Volume 457 - Workshop Italiano sulla Fisica  ad Alta Intensità (WIFAI2023) - session LFV
Lepton Flavour Universality tests at Belle II
G. Gaudino
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Pre-published on: March 12, 2024
Published on:
We present some recent tests of lepton universality with semileptonic decays of $B$-mesons. The analyses are based on data collected at the $\Upsilon(4S)$ resonance by the Belle II experiment, for an integrated luminosity of $189~\text{fb}^{-1}$.\\
This report includes two key analyses focusing on $\tau$ over $\mu/e$ lepton universality. The first is the measurement of the branching-fraction ratio $R(D^{*}_{\tau/\ell}) =\mathcal{B}(\overline{B} \to D^* \tau^-\overline{\nu}_e)/\mathcal{B}(\overline{B} \to D^*\ell^-\overline{\nu}_\mu)$ using hadronic tagging. The second is the first measurement of the inclusive ratio $R(X_{\tau/\ell})=\mathcal{B}(\overline{B} \to X \tau^-\overline{\nu}_e)/\mathcal{B}(\overline{B} \to X \ell^-\overline{\nu}_\mu)$.\\
We also present the branching-fraction ratios $R(X_{e/\mu})=\mathcal{B}(\overline{B} \to Xe^-\overline{\nu}_e)/\mathcal{B}(\overline{B} \to X\mu^-\overline{\nu}_\mu)$ and the first measurement of a comprehensive set of five angular asymmetries using $\overline{B^0}\to D^{^+}\ell^- \overline{\nu}_\ell$ decays.\\
All results presented are consistent with their corresponding Standard Model predictions and, where applicable, with the experimental world averages.
DOI: https://doi.org/10.22323/1.457.0019
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