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A bstract We 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 B ¯ events. The data were collected at the ϒ(4 S ) 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 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.

A bstract 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.

A bstract We report a new measurement of the e + e − → ϒ( nS ) π + 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 − 1.1 + 0.7 MeV / c 2 and Γ = 35.5 − 11.3 − 3.3 + 17.6 + 3.9 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 (1 S ) π + π − process at the energy 10 . 52 GeV, which is below the B B ¯ threshold.

A bstract We report a measurement of the electric dipole moment of the τ lepton ( dτ ) using an 833 fb − 1 data sample collected near the Υ(4 S ) resonance, with the Belle detector at the KEKB asymmetric-energy e + e − collider. Using an optimal observable method, we obtain the real and imaginary parts of d τ as Re( d τ ) = ( − 0 . 62 ± 0 . 63) × 10 − 17 e cm and Im( d τ ) = ( − 0 . 40 ± 0 . 32) × 10 − 17 e cm, respectively. These results are consistent with null electric dipole moment at the present level of experimental sensitivity and improve the sensitivity by about a factor of three.

A bstract Charged-lepton-flavor-violation is predicted in several new physics scenarios. We update the analysis of τ lepton decays into a light charged lepton ( ℓ = e ± or μ ± ) and a vector meson ( V 0 = ρ 0 , ϕ , ω , K *0 , or K ¯ *0 ) using 980 fb − 1 of data collected with the Belle detector at the KEKB collider. No significant excess of such signal events is observed, and thus 90% credibility level upper limits are set on the τ → ℓV 0 branching fractions in the range of (1.7–4 . 3) × 10 − 8 . These limits are improved by 30% on average from the previous results.

A bstract We present the first measurement of the branching fraction of the singly Cabibbo-suppressed (SCS) decay Λ c + → pη ′ with η ′ → ηπ + π − , using a data sample corresponding to an integrated luminosity of 981 fb − 1 , collected by the Belle detector at the KEKB e + e − asymmetric-energy collider. A significant Λ c + → pη ′ signal is observed for the first time with a signal significance of 5.4 σ . The relative branching fraction with respect to the normalization mode Λ c + → pK − π + is measured to be B Λ c + → pη ′ B Λ c + → pK − π + = 7.54 ± 1.32 ± 0.73 × 10 − 3 , where the uncertainties are statistical and systematic, respectively. Using the world-average value of B Λ c + → pK − π + = (6 . 28 ± 0 . 32) × 10 − 2 , we obtain B Λ c + → pη ′ = 4.73 ± 0.82 ± 0.46 ± 0.24 × 10 − 4 , where the uncertainties are statistical, systematic, and from B Λ c + → pK − π + , respectively.

A bstract We present a search for the lepton-flavor-violating decays B s 0 → ℓ ∓ τ ± , where ℓ = e, μ , using the full data sample of 121 fb − 1 collected at the Υ(5 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e − collider. We use B s 0 B ¯ s 0 events in which one B s 0 meson is reconstructed in a semileptonic decay mode and the other in the signal mode. We find no evidence for B s 0 → ℓ ∓ τ ± decays and set upper limits on their branching fractions at 90% confidence level as B ( B s 0 → e ∓ τ ± ) < 14 × 10 − 4 and B ( B s 0 → μ ∓ τ ± ) < 7 . 3 × 10 − 4 . Our result represents the first upper limit on the B s 0 → e ∓ τ ± decay rate.

A bstract We measure the cross section of e + e − → η c J/ψ at 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 in e + e − → η c J/ψ via initial state radiation near the η c J/ψ threshold. No evident signal of the double charmonium state is found, but evidence for the e + e − → η c J/ψ process is found with a statistical significance greater than 3 . 3 σ near the η c J/ψ threshold. The average cross section near the threshold is measured and upper limits of cross sections are set for other regions.

A bstract We report the measurement of the two-photon decay width of χ c 2 (1 P ) in two-photon processes at the Belle experiment. We analyze the process γγ → χ c 2 (1 P ) → J/ψγ , J/ψ → ℓ + ℓ − ( ℓ = e or μ ) using a data sample of 971 fb − 1 collected with the Belle detector at the KEKB e + e − collider. In this analysis, the product of the two-photon decay width of χ c 2 (1 P ) and the branching fraction is determined to be Γ γγ χ c 2 1 P B χ c 2 1 P → J / ψγ B J / ψ → ℓ + ℓ − = 14.8 ± 0.3 stat . ± 0.7 syst . eV, which corresponds to Γ γγ ( χ c 2 (1 P )) = 653 ± 13(stat.) ± 31(syst.) ± 17(B.R.) eV, where the third uncertainty is from B ( χ c 2 (1 P ) → J/ψγ ) and B ( J/ψ → ℓ + ℓ − ).

We present the first model-independent measurement of the CKM unitarity triangle angle ϕ3 using B±→ D(KS0\\[ {K}_{\\mathrm{S}}^0 \\]π+π−π0) K± decays, where D indicates either a D0 or D¯\\[ \\overline{D} \\]0 meson. Measurements of the strong-phase difference of the D →KS0\\[ {K}_{\\mathrm{S}}^0 \\]π+π−π0 amplitude obtained from CLEO-c data are used as input. This analysis is based on the full Belle data set of 772 × 106BB¯\\[ \\overline{B} \\] events collected at the Υ(4S) resonance. We obtain ϕ3 = (5.7−8.8+10.2\\[ {5.7}_{-8.8}^{+10.2} \\]±3.5±5.7)° and the suppressed amplitude ratio rB = 0.323±0.147±0.023±0.051. Here the first uncertainty is statistical, the second is the experimental systematic, and the third is due to the precision of the strong-phase parameters measured from CLEO-c data. The 95% confidence interval on ϕ3 is (−29.7, 109.5)°, which is consistent with the current world average.