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    Measurement of the branching fractions of Bˉ→D(∗)K−K(S)(∗)0\bar{B}\to D^{(*)} K^- K^{(*)0}_{(S)} and Bˉ→D(∗)Ds−\bar{B}\to D^{(*)}D_s^{-} decays at Belle II

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    International audienceWe present measurements of the branching fractions of eight B‾0→D(∗)+K−K(S)(∗)0\overline B{}^0\to D^{(*)+} K^- K^{(*)0}_{(S)}, B−→D(∗)0K−K(S)(∗)0B^{-}\to D^{(*)0} K^- K^{(*)0}_{(S)} decay channels. The results are based on data from SuperKEKB electron-positron collisions at the Υ(4S)\Upsilon(4S) resonance collected with the Belle II detector, corresponding to an integrated luminosity of 362 fb−1362~\text{fb}^{-1}. The event yields are extracted from fits to the distributions of the difference between expected and observed BB meson energy, and are efficiency-corrected as a function of m(K−K(S)(∗)0)m(K^-K^{(*)0}_{(S)}) and m(D(∗)K(S)(∗)0)m(D^{(*)}K^{(*)0}_{(S)}) in order to avoid dependence on the decay model. These results include the first observation of B‾0→D+K−KS0\overline B{}^0\to D^+K^-K_S^0, B−→D∗0K−KS0B^-\to D^{*0}K^-K_S^0, and B‾0→D∗+K−KS0\overline B{}^0\to D^{*+}K^-K_S^0 decays and a significant improvement in the precision of the other channels compared to previous measurements. The helicity-angle distributions and the invariant mass distributions of the K−K(S)(∗)0K^- K^{(*)0}_{(S)} systems are compatible with quasi-two-body decays via a resonant transition with spin-parity JP=1−J^P=1^- for the K−KS0K^-K_S^0 systems and JP=1+J^P= 1^+ for the K−K∗0K^-K^{*0} systems. We also present measurements of the branching fractions of four B‾0→D(∗)+Ds−\overline B{}^0\to D^{(*)+} D_s^-, B−→D(∗)0Ds−B^{-}\to D^{(*)0} D_s^- decay channels with a precision compatible to the current world averages
    Archives ouvertes de Paris-Saclay
    HAL-IN2P3
    HAL AMU
    DESY
    HAL

    Measurement of the branching fractions of B‾ \overline{B} → D(∗)^{(*)}K−K(S)(∗)0^{−} {K}_{(S)}^{\left(\ast \right)0} and B‾ \overline{B} → D(∗)Ds−^{(*)} {D}_s^{-} decays at Belle II

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    We present measurements of the branching fractions of eight B‾0 {\overline{B}}^0 → D(∗)+^{(*)+}K−K(S)(∗)0^{−} {K}_{(S)}^{\left(\ast \right)0} , B−^{−} → D(∗)0^{(*)0}K−K(S)(∗)0^{−} {K}_{(S)}^{\left(\ast \right)0} decay channels. The results are based on data from SuperKEKB electron-positron collisions at the Υ(4S) resonance collected with the Belle II detector, corresponding to an integrated luminosity of 362 fb−1^{−1}. The event yields are extracted from fits to the distributions of the difference between expected and observed B meson energy, and are efficiency-corrected as a function of m(K−K(S)(∗)0^{−} {K}_{(S)}^{\left(\ast \right)0} ) and m(D(∗)K(S)(∗)0^{(*)} {K}_{(S)}^{\left(\ast \right)0} ) in order to avoid dependence on the decay model. These results include the first observation of B‾0 {\overline{B}}^0 → D+^{+}K−KS0^{−} {K}_S^0 , B−^{−} → D*0^{0}K−KS0^{−} {K}_S^0 , and B‾0 {\overline{B}}^0 → D*+^{+}K−KS0^{−} {K}_S^0 decays and a significant improvement in the precision of the other channels compared to previous measurements. The helicity-angle distributions and the invariant mass distributions of the K−K(S)(∗)0^{−} {K}_{(S)}^{\left(\ast \right)0} systems are compatible with quasi-two-body decays via a resonant transition with spin-parity JP^{P} = 1−^{−} for the K−KS0^{−} {K}_S^0 systems and JP^{P} = 1+^{+} for the K−^{−}K*0^{0} systems. We also present measurements of the branching fractions of four B‾0 {\overline{B}}^0 → D(∗)+Ds−^{(*)+} {D}_s^{-} , B−^{−} → D(∗)0Ds−^{(*)0} {D}_s^{-} decay channels with a precision compatible to the current world averages.[graphic not available: see fulltext
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    Test of light-lepton universality in τ\tau decays with the Belle II experiment

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    International audienceWe present a measurement of the ratio Rμ=B(τ−→μ−νˉμντ)/B(τ−→e−νˉeντ)R_\mu = \mathcal{B}(\tau^-\to \mu^-\bar\nu_\mu\nu_\tau) / \mathcal{B}(\tau^-\to e^-\bar\nu_e\nu_\tau) of branching fractions B\mathcal{B} of the τ\tau lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB e+e−e^+e^- collider. The sample has an integrated luminosity of 362 fb−1^{-1} at a centre-of-mass energy of 10.58 GeV. Using an optimised event selection, a binned maximum likelihood fit is performed using the momentum spectra of the electron and muon candidates. The result, Rμ=0.9675±0.0007±0.0036R_\mu = 0.9675 \pm 0.0007 \pm 0.0036, where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to the WW boson in τ\tau decays of 0.9974±0.00190.9974 \pm 0.0019, in agreement with the standard model expectation of unity
    Archives ouvertes de Paris-Saclay
    HAL-IN2P3
    HAL AMU
    HAL

    Test of light-lepton universality in τ decays with the Belle II experiment

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    We present a measurement of the ratio Rμ=B(τ−→μ−ν‾μντ)/B(τ−→e−ν‾eντ) {R}_{\mu }=\mathcal{B}\left({\tau}^{-}\to {\mu}^{-}{\overline{\nu}}_{\mu }{\nu}_{\tau}\right)/\mathcal{B}\left({\tau}^{-}\to {e}^{-}{\overline{\nu}}_e{\nu}_{\tau}\right) of branching fractions B \mathcal{B} of the τ lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB e+^{+}e−^{−} collider. The sample has an integrated luminosity of 362 ± 2 fb−1^{−1} at a centre-of-mass energy of 10.58 GeV. Using an optimised event selection, a binned maximum likelihood fit is performed using the momentum spectra of the electron and muon candidates. The result, Rμ_{μ} = 0.9675 ± 0.0007 ± 0.0036, where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to the W boson in τ decays of 0.9974 ± 0.0019, in agreement with the standard model expectation of unity.[graphic not available: see fulltext
    DESY

    Test of light-lepton universality in τ\tau decays with the Belle II experiment

    Author
    Publication venue
    Publication date
    Field of study
    No full text
    We present a measurement of the ratio Rμ=B(τ−→μ−νˉμντ)/B(τ−→e−νˉeντ)R_\mu = \mathcal{B}(\tau^-\to \mu^-\bar\nu_\mu\nu_\tau) / \mathcal{B}(\tau^-\to e^-\bar\nu_e\nu_\tau) of branching fractions B\mathcal{B} of the τ\tau lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB e+e−e^+e^- collider. The sample has an integrated luminosity of 362 fb−1^{-1} at a centre-of-mass energy of 10.58 GeV. Using an optimised event selection, a binned maximum likelihood fit is performed using the momentum spectra of the electron and muon candidates. The result, Rμ=0.9675±0.0007±0.0036R_\mu = 0.9675 \pm 0.0007 \pm 0.0036, where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to the WW boson in τ\tau decays of 0.9974±0.00190.9974 \pm 0.0019, in agreement with the standard model expectation of unity
    DESY
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