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Belle~II results related to $b \to c$ anomalies
https://docs.belle2.org/record/3744
We report two new measurements for tests of lepton flavor universality between electrons and muons using semileptonic $B$ decays with a data set of $189~\mathrm{fb}^{-1}$ collected at the Belle II experiment between 2019 and 2021. Firstly, we find a ratio of inclusive branching fractions at $R(X_{e/\mu}) \equiv \mathcal{B}(\overline{B} \rightarrow Xe^{-}\overline{\nu}_{e})/\mathcal{B}(\overline{B} \rightarrow X\mu^{-}\overline{\nu}_{\mu}) = 1.007 \pm 0.009 (\mathrm{stat.}) \pm 0.019 (\mathrm{syst.})$. This inclusive measurement leads to the most precise universality test based on branching fractions. The measured $R(X_{e/\mu})$ is consistent with the Standard-Model prediction. Secondly, we measure a comprehensive set of five angular asymmetries of $\overline{B}^{0} \rightarrow {D^{*}}^{+}\ell^{-}\overline{\nu}_{\ell}$ decays and obtain agreements with the Standard Model for the measured asymmetries and their differences at a $p$-value above $13\%$. From both tests, no evidence of lepton universality violation is found.Kazuki KojimaTue, 18 Jul 2023 18:16:03 GMThttps://docs.belle2.org/record/37442023-07-17Belle~II results related to $b \to c$ anomalies
https://docs.belle2.org/record/3724
We report two novel measurements for tests of lepton flavor universality between electrons and muons using semileptonic $B$ decays with a data set of $189~\mathrm{fb}^{-1}$ collected at the Belle II experiment between 2019 and 2021. Firstly, we find a ratio of inclusive branching ratios at $R(X_{e/\mu}) \equiv \mathcal{B}(\overline{B} \rightarrow Xe^{-}\overline{\nu}_{e})/\mathcal{B}(\overline{B} \rightarrow X\mu^{-}\overline{\nu}_{\mu}) = 1.007 \pm 0.009 (\mathrm{stat.}) \pm 0.019 (\mathrm{syst.})$. This inclusive measurement leads to the most precise universality test based on branching ratios. The measured $R(X_{e/\mu})$ is consistent with the Standard-Model prediction. Secondly, we measure a comprehensive set of five angular asymmetries of $\overline{B}^{0} \rightarrow {D^{*}}^{+}\ell^{-}\overline{\nu}_{\ell}$ decays and obtain agreements with the Standard Model for the asymmetries at a $p$-value more than $13\%$. From both tests, no evidence of the universality violation is found.Kazuki KojimaMon, 10 Jul 2023 00:48:57 GMThttps://docs.belle2.org/record/37242023-07-10Belle II results related to b→c anomalies
https://docs.belle2.org/record/3486
Recent Belle II results of light-lepton flavor universality tests for b→c anomalies using semileptonic B decays are shown. This talk discusses the results of two measurements of $R(X_{e/\mu})$ and asymmetries of five angular observables between electron and muon, $\Delta\mathcal{A}_{x}(w)$, involving the hadronic tagging method in the Full Event Interpretation.Kazuki KojimaThu, 23 Mar 2023 18:53:30 GMThttps://docs.belle2.org/record/34862023-03-20SEARCH FOR B+ → K+νν DECAYS WITH AN INCLUSIVE TAGGING METHOD AT THE BELLE II EXPERIMENT
https://docs.belle2.org/record/2369
This contribution illustrates a new search for the flavor-changing neutral-current decay B+ → K+νν performed by the Belle II experiment at the SuperKEKB asymmetric-energy electron-positron collider. In this study, a sample corresponding to an integrated luminosity of 63 fb−1 collected at the Υ(4S) resonance and an additional sample of 9 fb−1 collected at an energy 60 MeV below the resonance are used. A novel technique, based on an inclusive tagging method and exploiting the topological features of the B+ → K+νν decay, is employed and it provides a higher signal efficiency with respect to the methods used in the previous searches. No significant signal is observed. An upper limit of 4.1 × 10−5 is set on the B+ → K+νν branching fraction at the 90 % confidence level.Filippo DattolaWed, 12 May 2021 16:16:35 GMThttps://docs.belle2.org/record/23692021-05-12