We report measurements of the charmless semileptonic decays B0→π−/ρ−ℓ+ν and B+→π0/ρ0ℓ+ν, based on a sample of 2.75×108BB¯ events collected at the ϒ(4S) resonance with the Belle detector at the KEKB ...e+e− asymmetric collider. In this analysis, the accompanying B meson is reconstructed in the semileptonic mode B→D(∗)ℓν, enabling detection of the signal modes with high purity. We measure the branching fractions B(B0→π−ℓ+ν)=(1.38±0.19±0.14±0.03)×10−4, B(B0→ρ−ℓ+ν)=(2.17±0.54±0.31±0.08)×10−4, B(B+→π0ℓ+ν)=(0.77±0.14±0.08±0.00)×10−4 and B(B+→ρ0ℓ+ν)=(1.33±0.23±0.17±0.05)×10−4, where the errors are statistical, experimental systematic, and systematic due to form factor uncertainties, respectively. For each mode we also present the partial branching fractions in three q2 intervals: q2<8, 8⩽q2<16, and q2⩾16 GeV2/c2. From our partial branching fractions for B→πℓν and recent results for the form factor from unquenched Lattice QCD calculations, we obtain values of the CKM matrix element |Vub|.
We study the baryonic charmonium decays of B mesons B+-->etacK+ and B+-->J/psiK+, where the etac and J/psi subsequently decay into a ppover or LambdaLambdaover pair. We measure the J/psi-->ppover and ...LambdaLambdaover anisotropy parameters alphaB=-0.60+/-0.13+/-0.14 (ppover), -0.44+/-0.51+/-0.31 (LambdaLambdaover ) and compare to results from e;{+}e;{-}-->J/psi formation experiments. We also report the first observation of etac-->LambdaLambdaover. The measured branching fraction is B(etac-->LambdaLambdaover )=(0.87(+0.24)/(-0.21)(stat)(+0.09/-0.14) (syst)+/-0.27(PDG))x10-3. This study is based on a 357 fb-1 data sample recorded on the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+ e- collider.
We present the first evidence of the decay B- --> tau- nu(tau), using 414 fb(-1) of data collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+ e- collider. ...Events are tagged by fully reconstructing one of the B mesons in hadronic modes. We detect the signal with a significance of 3.5 standard deviations including systematics and measure the branching fraction to be B(B- --> tau- nu(tau)) = (1.79(-0.49) +0.56(stat)(-0.51) +0.46(syst)) x 10(-4). This implies that fB = 0.229(-0.031) +0.036(stat)(-0.037) +0.034(syst) GeV and is the first direct measurement of this quantity.
Using a sample of 152 x 10(6) BB pairs accumulated with the Belle detector at the KEKB e+e- collider, we study the decay mechanism of three-body charmed decay B- --> Lambdac+ ppi-. The intermediate ...two-body decay B--->Sigmac (2455)0 p is observed for the first time with a branching fraction of (3.7 +/- 0.7 +/- 0.4 +/- 1.0) x 10(-5) and a statistical significance of 8.4sigma. We also observe a low-mass enhancement in the (Lambdac+p) system, which can be parametrized as a Breit-Wigner function with a mass of (3.35(-0.02)(+0.01) +/-0.02) GeV/c2 and a width of (0.07(-0.03)(+0.04) +/-0.04) GeV/c2. We measure its branching fraction to be (3.9(-0.7)(+0.8) +/- 0.4 +/- 1.0) x 10(-5) with a statistical significance of 6.2sigma. The errors are statistical, systematic, and that of the Lambdac+-->pK- pi+ decay branching fraction.
We report the first observation of two charmed strange baryons that decay into Lambda(c)(+)Kappa(-)pi(+). The broader of the two states is measured to have a mass of 2978.5+/-2.1+/-2.0 MeV/c2 and a ...width of 43.5+/-7.5+/-7.0 MeV/c2. The mass and width of the narrow state are measured to be 3076.7+/-0.9+/-0.5 MeV/c;{2} and 6.2+/-1.2+/-0.8 MeV/c2, respectively. We also perform a search for the isospin partner states that decay into Lambda(c)(+)Kappa(0)/(s)pi(-) and observe a significant signal at the mass of 3082.8+/-1.8+/-1.5 MeV/c2. The data used for this analysis were accumulated at or near the Upsilon(4S) resonance, using the Belle detector at the e+ e- asymmetric-energy collider KEKB. The integrated luminosity of the data sample used is 461.5 fb(-1).
PDF
