Measurement of B(Bs_{s} →ds_{s}X) with Bs_{s} semileptonic tagging

We report the first direct measurement of the inclusive branching fraction B(B$_{s}$ →D$_{s}$X) via B$_{s}$ tagging in e$^{+}$e$^{–}$→Υ(5S) events. Tagging is accomplished through a partial reconstruction of semileptonic decays B$_{s}$→D$_{s}$Xℓν, where X denotes unreconstructed additional hadrons or photons and ℓ is an electron or muon. With 121.4 fb$^{–1}$ of data collected at the Υ(5S) resonance by the Belle detector at the KEKB asymmetric-energy e$^{+}$e$^{–}$ collider, we obtain B(B$_{s}$ →D$_{s}$X)=(60.2±5.8±2.3)%, where the first uncertainty is statistical and the second is systematic

Observation of the Radiative Decays of Υ(1S) to Χc1_{c1}

We report the first observation of the radiative decay of the $\Upsilon(1S)$ into a charmonium state. The statistical significance of the observed signal of $\Upsilon(1S) \to \gamma \chi_{c1}$ is 6.3 standard deviations including systematics. The branching fraction is calculated to be Br($\Upsilon(1S) \to \gamma \chi_{c1}$) = (4.7^{+2.4}_{-1.8} (stat) ^{+0.4}_{-0.5} (sys)) * 10^{-5}. We also searched for $\Upsilon(1S)$ radiative decays into $\chi_{c0,2}$ and $\eta_c(1S,2S)$ and set upper limits on their branching fractions. These results are obtained from a 24.9 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider at a center-of-mass energy equal to the $\Upsilon(2S)$ mass using $\Upsilon(1S)$ tagging by the $\Upsilon(2S) \to \Upsilon(1S) \pi^+\pi^-$ transitions

Observation of a new structure near 10.75 GeV in the energy dependence of the e+e−→ ϒ (nS)π+π− (n = 1, 2, 3) cross sections

We report a new measurement of the e$^{+}$e$^{-}$→ ϒ(nS)π$^{+l}$π$^{-}$ (n = 1, 2, 3) cross sections at energies from 10.52 to 11.02 GeV using data collected with the Belle detector at the KEKB asymmetric-energy e$^{+}$e$^{-}$ collider. We observe a new structure in the energy dependence of the cross sections; if described by a Breit-Wigner function its mass and width are found to be M=(10752.7±5.9$^{+0.7}$$_{-1.1}$)MeV/c$^{2}$ and Γ=(35.5$^{+17.6+3.9}$$_{−11.3−3.3}$)MeV, where the first error is statistical and the second is systematic. The global significance of the new structure including systematic uncertainty is 5.2 standard deviations. We also find evidence for the e$^{+}$e$^{-}$→ ϒ (1S) π$^{+l}$π$^{-}$ process at the energy 10.52 GeV, which is below the BB̅ threshold

Measurement of Two-Particle Correlations of Hadrons in e⁺ e⁻ Collisions at Belle

The measurement of two-particle angular correlation functions in high-multiplicity e+e− collisions at √s=10.52  GeV is reported. In this study, the 89.5  fb−1 of hadronic e+e− annihilation data collected by the Belle detector at KEKB are used. Two-particle angular correlation functions are measured in the full relative azimuthal angle (Δϕ) and three units of pseudorapidity (Δη), defined by either the electron beam axis or the event-shape thrust axis, and are studied as a function of charged-particle multiplicity. The measurement in the thrust axis analysis, with mostly outgoing quark pairs determining the reference axis, is sensitive to the region of additional soft gluon emissions. No significant anisotropic collective behavior is observed with either coordinate analyses. Near-side jet correlations appear to be absent in the thrust axis analysis. The measurements are compared to predictions from various event generators and are expected to provide new constraints to the phenomenological models in the low-energy regime

Search for B⁰ meson decays into Λ and missing energy with a hadronic tagging method at Belle

We present a search for the decays of B0 mesons into a final state containing a Λ baryon and missing energy. These results are obtained from a 711  fb−1 data sample that contains 772×106  B¯B pairs and was collected near the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. We use events in which one B meson is fully reconstructed in a hadronic decay mode and require the remainder of the event to consist of only a single Λ. No evidence for these decays is found, and we set 90% confidence level upper limits on the branching fractions in the range 2.1–3.8×10−5. This measurement provides the world’s most restrictive limits, with implications for baryogenesis and dark matter production

Search for the decay Bs_{s}0^{0} →ηη

We report results from a search for the decay B$_{s}$$^{0}$ →ηη using 121.4 fb$^{-1}$ of data collected at the Υ(5S) resonance with the Belle detector at the KEKB asymmetric-energy e$^{+}$e$^{-}$ collider. We do not observe any signal and set an upper limit on the branching fraction of 14.3×10$^{-5}$ at 90% confidence level. This result represents a significant improvement over the previous most stringent limit

Measurement of the energy dependence of the e+^{+}e−^{-} → BB‾ B\overline{B} , BB‾∗ B{\overline{B}}^{\ast } and B∗B‾∗ {B}^{\ast }{\overline{B}}^{\ast } exclusive cross sections

Abstract We report the first measurement of the exclusive cross sections e + e − → B B ¯ $$B\overline{B}$$ , e + e − → B B ¯ ∗ $$B{\overline{B}}^{\ast }$$ , and e + e − → B ∗ B ¯ ∗ $${B}^{\ast }{\overline{B}}^{\ast }$$ in the energy range from 10.63 GeV to 11.02 GeV. The B mesons are fully reconstructed in a large number of hadronic final states and the three channels are identified using a beam-constrained-mass variable. The shapes of the exclusive cross sections show oscillatory behavior with several maxima and minima. The results are obtained using data collected by the Belle experiment at the KEKB asymmetric-energy e + e − collider