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We measure the complete set of angular coefficients for exclusive decays ( , ). Our analysis uses the full Belle dataset with hadronic tag-side reconstruction. The results allow us to extract the form factors describing the transition and the Cabibbo-Kobayashi-Maskawa matrix element . Using recent lattice QCD calculations for the hadronic form factors, we find using the Boyd-Grinstein-Lebed parametrization, compatible with determinations from inclusive semileptonic decays. We search for lepton flavor universality violation as a function of the hadronic recoil parameter and investigate the differences of the electron and muon angular distributions. We find no deviation from standard model expectations. Published by the American Physical Society2024
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A<sc>bstract</sc> We report a search for the charged-lepton flavor violation in Υ(2S) →ℓ∓τ±(ℓ=e, μ) decays using a 25 fb−1Υ(2S) sample collected by the Belle detector at the KEKBe+e−asymmetric-energy collider. We find no evidence for a signal and set upper limits on the branching fractions ($$ \mathcal{B} $$ ) at 90% confidence level. We obtain the most stringent upper limits:$$ \mathcal{B} $$ (Υ(2S)→ μ∓τ±)<0.23×10−6and$$ \mathcal{B} $$ (Υ(2S)→ e∓τ±)<1.12×10−6.more » « less
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A<sc>bstract</sc> We measure the cross section ofe+e−→ηcJ/ψat the Υ(nS)(n= 1–5) on-resonance and 10.52 GeV off-resonance energy points using the full data sample collected by the Belle detector with an integrated luminosity of 955 fb−1. We also search for double charmonium production ine+e−→ηcJ/ψvia initial state radiation near theηcJ/ψthreshold. No evident signal of the double charmonium state is found, but evidence for thee+e−→ ηcJ/ψprocess is found with a statistical significance greater than 3.3σnear theηcJ/ψthreshold. The average cross section near the threshold is measured and upper limits of cross sections are set for other regions.more » « less
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A<sc>bstract</sc> We report the first measurement of the inclusivee+e−→$$ b\overline{b} $$ →$$ {D}_s^{\pm } $$ Xande+e−→$$ b\overline{b} $$ → D0/$$ {\overline{D}}^0 $$ Xcross sections in the energy range from 10.63 to 11.02 GeV. Based on these results, we determineσ(e+e−→$$ {B}_s^0{\overline{B}}_s^0 $$ X) andσ(e+e−→$$ B\overline{B} $$ X) in the same energy range. We measure the fraction of$$ {B}_s^0 $$ events at Υ(10860) to befs= ($$ {22.0}_{-2.1}^{+2.0} $$ )%. We determine also the ratio of the$$ {B}_s^0 $$ inclusive branching fractions$$ \mathcal{B} $$ ($$ {B}_s^0 $$ → D0/$$ {\overline{D}}^0 $$ X)/$$ \mathcal{B} $$ ($$ {B}_s^0 $$ →$$ {D}_s^{\pm } $$ X) = 0.416 ± 0.018 ± 0.092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energye+e−collider.more » « less
