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

Search for the decay B0^0 → K∗0^{ *0} τ+^+ τ−^− at the Belle experiment

This paper presents a search for the rare flavor-changing neutral current process $B^0→K^{*0}τ^+τ^−$ using data taken with the Belle detector at the KEKB asymmetric energy $e^+e^−$ collider. The analysis is based on the entire $Υ(4S)$ resonance data sample of $711  fb^{−1}$, corresponding to $772×10^6B\bar{B}$ pairs. In our search we fully reconstruct the companion B meson produced in the process $e^+e^−→Υ(4S)→B\bar{B}$ from its hadronic decay modes, and look for the decay $B^0→K^{*0}τ^+τ^−$ in the rest of the event. No evidence for a signal is found. We report an upper limit on the branching fraction $\mathcal{B}(B^0→K^{*0}τ^+τ^−)<3.1×10^{−3}$ at 90% confidence level. This is the first direct limit on $\mathcal{B}(B^0→K^{*0}τ^+τ^−)$

Search for lepton-flavor-violating tau-lepton decays to ℓγ at Belle

Charged lepton flavor violation is forbidden in the Standard Model but possible in several new physics scenarios. In many of these models, the radiative decays τ$^{±}$ → ℓ$^{±}$γ (ℓ = e, μ) are predicted to have a sizeable probability, making them particularly interesting channels to search at various experiments. An updated search via τ$^{±}$ → ℓ$^{±}$γ using full data of the Belle experiment, corresponding to an integrated luminosity of 988 fb$^{-1}$, is reported for charged lepton flavor violation. No significant excess over background predictions from the Standard Model is observed, and the upper limits on the branching fractions, B(τ$^{±}$ → μ$^{±}$γ) ≤ 4.2 × 10$^{-8}$ and B(τ$^{±}$ → e$^{±}$γ) ≤ 5.6 × 10$^{-8}$, are set at 90% confidence level

Measurement of Differential Branching Fractions of Inclusive B →xu_{u}ℓ+^{+}νℓ_{ℓ} Decays

The first measurements of differential branching fractions of inclusive semileptonic B → X$_{u}$ℓ$^{+}$ν$_{ℓ}$ decays are performed using the full Belle data set of 711 fb$^{-1}$ of integrated luminosity at the Υ(4S) resonance and for ℓ=e, μ. With the availability of these measurements, new avenues for future shape-function model-independent determinations of the Cabibbo-Kobayashi Maskawa matrix element |Vx$_{ub}$| can be pursued to gain new insights in the existing tension with respect to exclusive determinations. The differential branching fractions are reported as a function of the lepton energy, the four-momentum-transfer squared, light-cone momenta, the hadronic mass, and the hadronic mass squared. They are obtained by subtracting the backgrounds from semileptonic B → X$_{u}$ℓ$^{+}$ν$_{ℓ}$ decays and other processes, and corrected for resolution and acceptance effects

Measurement of the mass and width of the Λc(2625)+\Lambda_c(2625)^+ and the branching ratios of Λc(2625)+→Σc0π+\Lambda_c(2625)^+ \to \Sigma_c^{0}\pi^{+} and Λc(2625)+→Σc++π−\Lambda_c(2625)^+ \to \Sigma_c^{++}\pi^{-}

Using the entire data sample of $980\,\textrm{fb}^{-1}$ collected with the Belle detector operating at the KEKB asymmetric-energy collider, we report the measurement of the mass, width, and the relative branching ratios of the $\Lambda_c(2625)^+$ charmed baryon. The mass difference between $\Lambda_c(2625)^+$ and $\Lambda_c^+$ is measured to be $M(\Lambda_c(2625)^{+}) - M(\Lambda_c^{+}) = 341.518 \pm 0.006 \pm 0.049\ \mathrm{MeV}/\mathit{c}^2$. The upper limit on the width is measured to be $\Gamma(\Lambda_c(2625)^+) < 0.52\,\mathrm{MeV}/\textit{c}^2$ at 90\% credibility level. Based on a full Dalitz plot fit, branching ratios with respect to the mode $\Lambda_c(2625)^+ \to \Lambda_c^+ \pi^+ \pi^-$ are measured to be $\frac{\mathcal{B}(\Lambda_c(2625)^+ \to \Sigma_c^{0} \pi^{+})} {\mathcal{B}(\Lambda_c(2625)^+ \to \Lambda_c^+ \pi^{+} \pi^{-})} = (5.19 \pm 0.23 \pm 0.40) \%$ and $\frac{\mathcal{B}(\Lambda_c(2625)^+ \to \Sigma_c^{++} \pi^{-})} {\mathcal{B}(\Lambda_c(2625)^+ \to \Lambda_c^+ \pi^{+} \pi^{-})} = (5.13 \pm 0.26 \pm 0.32) \%$. These measurements can be used to further constrain the parameters of the underlying theoretical models

Search for the ηc2_{c2}(1D) in e⁺e⁻ → γηc2_{c2}(1D) at √s near 10.6 GeV at Belle

For the first time we search for the η$_{c2}$(1D) in e$^{+}$e$^{-}$→γη$_{c2}$(1D) at $\sqrt{s}$=10.52, 10.58, and 10.867 GeV with data samples of 89.5  fb$^{-1}$, 711  fb$^{-1}$, and 121.4  fb$^{-1}$, respectively, accumulated with the Belle detector at the KEKB asymmetric energy electron-positron collider. No significant η$_{c2}$(1D) signal is observed in the mass range between 3.8 and 3.88  GeV/c2. The upper limit at 90% confidence level on the product of the Born cross section for e+e−→γηc2(1D) and branching fraction for η$_{c2}$(1D)→γh$_{c}$(1P) is determined to be σ(e$^{+}$e$^{-}$→γη$_{c2}$(1D))B(η$_{c2}$(1D)→γh$_{c}$(1P))<4.9  fb at $\sqrt{s}$ near 10.6 GeV