With the full data sample of 772×106 BB¯ pairs recorded by the Belle detector at the KEKB electron-positron collider, the decay B¯→D*τ−ν¯τ is studied with the hadronic τ decays τ−→π−ντ and τ−→ρ−ντ. ...The τ polarization Pτ(D*) in two-body hadronic τ decays is measured, as well as the ratio of the branching fractions R(D*)=B(B¯→D*τ−ν¯τ)/B(B¯→D*ℓ−ν¯ℓ), where ℓ− denotes an electron or a muon. Our results, Pτ(D*)=−0.38±0.51(stat)−0.16+0.21(syst) and R(D*)=0.270±0.035(stat)−0.025+0.028(syst), are consistent with the theoretical predictions of the standard model. The polarization values of Pτ(D*)>+0.5 are excluded at the 90% confidence level.
We present a new measurement of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| from B0→D*−ℓ+νℓ decays, reconstructed with the full Belle data set of 711 fb−1 integrated luminosity. Two form ...factor parametrizations, originally conceived by the Caprini-Lellouch-Neubert (CLN) and the Boyd, Grinstein and Lebed (BGL) groups, are used to extract the product F(1)ηEW|Vcb| and the decay form factors, where F(1) is the normalization factor and ηEW is a small electroweak correction. In the CLN parametrization we find F(1)ηEW|Vcb|=(35.06±0.15±0.56)×10−3, ρ2=1.106±0.031±0.007, R1(1)=1.229±0.028±0.009, R2(1)=0.852±0.021±0.006. For the BGL parametrization we obtain F(1)ηEW|Vcb|=(34.93±0.23±0.59)×10−3, which is consistent with the world average when correcting for F(1)ηEW. The branching fraction of B0→D*−ℓ+νℓ is measured to be B(B0→D*−ℓ+νℓ)=(4.90±0.02±0.16)%. We also present a new test of lepton flavor universality violation in semileptonic B decays, B(B0→D*−e+ν)B(B0→D*−μ+ν)=1.01±0.01±0.03. The errors quoted correspond to the statistical and systematic uncertainties, respectively. This is the most precise measurement of F(1)ηEW|Vcb| and form factors to date and the first experimental study of the BGL form factor parametrization in an experimental measurement.
Using the entire Belle data sample of 980 fb−1 of e+e− collisions, we present the results of a study of excited Ωc charmed baryons in the decay mode Ξc+K−. We show confirmation of four of the five ...narrow states reported by the LHCb Collaboration: the Ωc(3000), Ωc(3050), Ωc(3066), and Ωc(3090).
We present a determination of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| using the decay B → Dℓνℓ (ℓ = e,μ) based on 711 fb–1 of e+e– → Υ(4S) data recorded by the Belle ...detector and containing 772 × 106 BB¯ pairs. Here, one B meson in the event is fully reconstructed in a hadronic decay mode, while the other, on the signal side, is partially reconstructed from a charged lepton and either a D+ or D0 meson in a total of 23 hadronic decay modes. The isospin-averaged branching fraction of the decay B → Dℓνℓ is found to be B(B0 → D–ℓ+νℓ) = (2.31 ± 0.03(stat) ± 0.11(syst))%. Analyzing the differential decay rate as a function of the hadronic recoil with the parametrization of Caprini, Lellouch, and Neubert and using the form-factor prediction G(1) = 1.0541 ± 0.0083 calculated by FNAL/MILC, we obtain ηEW|Vcb| = (40.12 ± 1.34) × 10–3, where ηEW is the electroweak correction factor. Alternatively, assuming the model-independent form-factor parametrization of Boyd, Grinstein, and Lebed and using lattice QCD data from the FNAL/MILC and HPQCD collaborations, we find ηEW|Vcb| = (41.10 ± 1.14) × 10–3.
We report the results of a search for the rare, purely leptonic decay B−→μ−ν¯μ performed with a 711 fb−1 data sample that contains 772×106 BB¯ pairs, collected near the ϒ(4S) resonance with the ...Belle detector at the KEKB asymmetric-energy e+e− collider. The signal events are selected based on the presence of a high momentum muon and the topology of the rest of the event showing properties of a generic B-meson decay, as well as the missing energy and momentum being consistent with the hypothesis of a neutrino from the signal decay. We find a 2.4 standard deviation excess above background including systematic uncertainties, which corresponds to a branching fraction of B(B−→μ−ν¯μ)=(6.46±2.22±1.60)×10−7 or a frequentist 90% confidence level interval on the B−→μ−ν¯μ branching fraction of 2.9,10.7×10−7.
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