Measurements of branching fraction and CPCP asymmetry of the Bˉ0(B0)→KS0K∓π±\bar{B}^{0}(B^{0})\to K^{0}_{S}K^{\mp}\pi^{\pm} decay at Belle

International audienceWe report the measurement of the branching fraction and $CP$ asymmetry for the $\bar{B}^{0}(B^{0})\to K^{0}_{S}K^{\mp}\pi^{\pm}$ decay. The analysis is performed on a data sample of 711 $\rm{fb}^{-1}$ collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. We obtain a branching fraction of $(3.60\pm0.33\pm0.15)\times10^{-6}$ and an $\mathcal{A}_{CP}$ of $(-8.5\pm8.9\pm0.2)\%$, where the first uncertainties are statistical and the second are systematic. Hints of peaking structures are also observed in the differential branching fraction as functions of Dalitz variables

Measurement of R(D)\mathcal{R}(D) and R(D∗)\mathcal{R}(D^{\ast}) with a semileptonic tagging method

We report a measurement of the ratios of branching fractions $\mathcal{R}(D) = {\cal B}(\bar{B} \to D \tau^- \bar{\nu}_{\tau})/{\cal B}(\bar{B} \to D \ell^- \bar{\nu}_{\ell})$ and $\mathcal{R}(D^{\ast}) = {\cal B}(\bar{B} \to D^* \tau^- \bar{\nu}_{\tau})/{\cal B}(\bar{B} \to D^* \ell^- \bar{\nu}_{\ell})$, where $\ell$ denotes an electron or a muon. The results are based on a data sample containing $772\times10^6$ $B\bar{B}$ events recorded at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. The analysis utilizes a method where the tag-side $B$ meson is reconstructed in a semileptonic decay mode, and the signal-side $\tau$ is reconstructed in a purely leptonic decay. The measured values are $\mathcal{R}(D)= 0.307 \pm 0.037 \pm 0.016$ and $\mathcal{R}(D^{\ast})= 0.283 \pm 0.018 \pm 0.014$, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within $0.2$ and $1.1$ standard deviations, respectively, while their combination agrees with the Standard Model predictions within $1.2$ standard deviations

Test of lepton flavor universality and search for lepton flavor violation in B→KℓℓB \rightarrow K\ell \ell decays

International audienceWe present measurements of the branching fractions for the decays B → Kμ$^{+}$μ$^{−}$ and B → Ke$^{+}$e$^{−}$, and their ratio (R$_{K}$), using a data sample of 711 fb$^{−1}$ that contains 772 × 10$^{6} B\overline{B}$ events. The data were collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e$^{+}$e$^{−}$ collider. The ratio R$_{K}$ is measured in five bins of dilepton invariant-mass-squared (q$^{2}$): q$^{2}$ ∈ (0.1, 4.0), (4.00, 8.12), (1.0, 6.0), (10.2, 12.8) and (> 14.18) GeV$^{2}$/c$^{4}$, along with the whole q$^{2}$ region. The R$_{K}$ value for q$^{2}$ ∈ (1.0, 6.0) GeV$^{2}$/c$^{4}$ is ${1.03}_{-0.24}^{+0.28}$ ± 0.01. The first and second uncertainties listed are statistical and systematic, respectively. All results for R$_{K}$ are consistent with Standard Model predictions. We also measure CP-averaged isospin asymmetries in the same q$^{2}$ bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the q$^{2}$ ∈ (1.0, 6.0) GeV$^{2}$/c$^{4}$ bin in the mode with muon final states. The measured differential branching fractions, $d\mathrm{\mathcal{B}}$/dq$^{2}$, are consistent with theoretical predictions for charged B decays, while the corresponding values are below the expectations for neutral B decays. We have also searched for lepton-flavor-violating B → Kμ$^{±}$e$^{∓}$ decays and set 90% confidence-level upper limits on the branching fraction in the range of 10$^{−8}$ for B$^{+}$ → K$^{+}$μ$^{±}$e$^{∓}$, and B$^{0}$ → K$^{0}$μ$^{±}$e$^{∓}$ modes.[graphic not available: see fulltext

Test of lepton flavor universality in B→K∗ℓ+ℓ−{B\to K^\ast\ell^+\ell^-} decays at Belle

We present a measurement of $R_{K^{\ast}}$, the ratio of the branching fractions ${\cal B}(B\to K^\ast \mu^+ \mu^-)$ and ${\cal B}(B\to K^\ast e^+ e^-)$, for both charged and neutral $B$ mesons. The ratio for charged $B$ mesons, $R_{K{^{\ast +}}}$, is the first measurement ever performed. The analysis is based on a data sample of $711~\mathrm{fb}^{-1}$, containing $772\times 10^{6}$ $B\bar B$ events, recorded at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider

Measurement of the D∗−D^{\ast-} polarization in the decay B0→D∗−τ+ντB^0 \to D^{\ast -}\tau^+\nu_{\tau}

International audienceWe report the first measurement of the $D^{\ast -}$ meson polarization in the decay $B^0 \to D^{*-} \tau^+\nu_{\tau}$ using the full data sample of 772$\times 10^6$ $B\bar{B}$ pairs recorded with the Belle detector at the KEKB electron-positron collider. Our result, $F_L^{D^\ast} = 0.60 \pm 0.08 ({\rm stat}) \pm 0.04 ({\rm sys})$, where $F_L^{D^\ast}$ denotes the $D^{\ast-}$ meson longitudinal polarization fraction, agrees within about $1.7$ standard deviations of the standard model prediction

Study of χbJ(nP)→ωΥ(1S)\chi_{bJ}(nP) \rightarrow \omega \Upsilon(1S) at Belle

We report results from a study of hadronic transitions of the $\chi_{bJ}(nP)$ states of bottomonium at Belle. The $P$-wave states are reconstructed in transitions to the $\Upsilon(1S)$ with the emission of an $\omega$ meson. The transitions of the $n=2$ triplet states provide a unique laboratory in which to study nonrelativistic quantum chromodynamics, as the kinematic threshold for production of an $\omega$ and $\Upsilon(1S)$ lies between the $J=0$ and $J=1$ states. A search for the $\chi_{bJ}(3P)$ states is also reported

Rediscovery of B0→J/ψKL0B^0 \rightarrow J/\psi K^0_L at Belle II

We present preliminary results on the reconstruction of the $B^0\to J\mskip 1mu / \psi\mskip 2mu K^0_{\scriptscriptstyle L}$ decay, where $J\mskip 1mu / \psi\mskip 2mu\to\mu^+\mu^-$ or $e^+e^-$. Using a dataset corresponding to a luminosity of 62.8\pm0.6\mbox{fb}^{-1} collected by the Belle II experiment at the SuperKEKB asymmetric energy $e^+e^-$ collider, we measure a total of $267\pm21$ candidates with $J\mskip 1mu / \psi\mskip 2mu\to\mu^+\mu^-$ and $226\pm20$ with with $J\mskip 1mu / \psi\mskip 2mu\to e^+e^-$. The quoted errors are statistical only