3,177 research outputs found

    Search for the X(1812) in B±K±ωϕB^{\pm} \to K^{\pm} \omega \phi

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    We report on a search for the X(1812) state in the decay B±K±ωϕB^{\pm} \to K^{\pm} \omega \phi with a data sample of 657×106657\times10^6 BBˉB\bar{B} pairs collected with the Belle detector at the KEKB e+ee^+e^- collider. No significant signal is observed. An upper limit B(B±K±X(1812),X(1812)ωϕ)<3.2×107{\cal B}(B^{\pm} \to K^{\pm} X(1812),X(1812) \to \omega \phi)<3.2\times 10^{-7} (90% C.L.) is determined. We also constrain the three-body decay branching fraction to be B(B±K±ωϕ){\cal B}(B^{\pm} \to K^{\pm} \omega \phi) << 1.9 ×106\times 10^{-6} (90% C.L.).Comment: 5pages,2 figures(3 figure files). submitted to PRD(RC

    Study of J/psi to p pbar, Lambda Lambdabar and observation of eta_c to Lambda Lambdabar at Belle

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    We study the baryonic charmonium decays of B mesons, B+ to etac K+ and B+ to J/psi K+, where the etac and J/psi subsequently decay into a p pbar or Lambda Lambdabar pair. We measure the J/psi to p pbar, Lambda Lambdabar anisotropy parameters, alpha_B = -0.60 +- 0.13 +-0.14 (p pbar), -0.44 +- 0.51 +- 0.31 (Lambda Lambdabar) and compare to results from e+e- to J/psi formation experiments. We also report the first observation of etac to Lambda Lambdabar. The measured branching fraction is B(etac to Lambda Lambdabar) = (0.87 +0.24 -0.21(stat) +0.09 -0.14(syst) +- 0.27 (PDG)) x 10^-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.Comment: 8 pages, two figures (4 figure files), an update of hep-ex/0509020 for journal submissio

    Search for CP Violation in the Decays D0KS0P0D^0\rightarrow K^0_S P^0

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    We have searched for CP violation in the decays D0KS0P0D^0\rightarrow K^0_S P^0 where P0P^0 denotes a neutral pseudo-scalar meson which is either a π0\pi^0, η\eta, or η\eta' using KEKB asymmetric-energy e+ee^+e^- collision data corresponding to an integrated luminosity of 791 fb1^{-1} collected with the Belle detector. No evidence of significant CP violation is observed. We report the most precise CP asymmetry measurement in the decay D0KS0π0D^0\rightarrow K^0_S\pi^0 to date: ACPD0KS0π0=(0.28±0.19±0.10)A_{CP}^{D^0\rightarrow K^0_S\pi^0}=(-0.28\pm0.19\pm0.10)%. We also report the first measurements of CP asymmetries in the decays D0KS0ηD^0\rightarrow K^0_S\eta and D0KS0ηD^0\rightarrow K^0_S\eta': ACPD0KS0η=(+0.54±0.51±0.16)A_{CP}^{D^0\rightarrow K^0_S\eta}=(+0.54\pm0.51\pm0.16)% and ACPD0KS0η=(+0.98±0.67±0.14)A_{CP}^{D^0\rightarrow K^0_S\eta'}=(+0.98\pm0.67\pm0.14)%, respectively

    Observation of Radiative Decay D0ϕγD^0 \to \phi \gamma

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    We report the observation of the decay D0ϕγD^{0} \to \phi \gamma with a statistical significance of 5.4σ5.4\sigma in 78.1 \ifb of data collected by the Belle experiment at the KEKB e+ee^+ e^- collider. This is the first observation of a flavor-changing radiative decay of a charmed meson. The Cabibbo- and color-suppressed decays D0ϕπ0D^0 \to \phi \pi^0, ϕη\phi \eta are also observed for the first time. We measure branching fractions \br(D^{0} \to \phi \gamma) = [ 2.60^{+0.70}_{-0.61} \stat {}^{+0.15}_{-0.17} \syst ] \times 10^{-5}, \br(D^{0} \to \phi \pi^{0}) = [ 8.01 \pm 0.26 \stat \pm 0.47 \syst ] \times 10^{-4}, and \br(D^{0} \to \phi \eta) = [ 1.48 \pm 0.47 \stat \pm 0.09 \syst ] \times 10^{-4}.Comment: 9 pages, 4 figures, Belle Preprint 2003-24, KEK Preprint 2003-75, updated version of BELLE-CONF-0346 (contributed paper to the XXI International Symposium on Lepton and Photon Interactions at High Energies,Fermilab Aug 11-16,2003). to appear in Phys. Rev. Let

    Measurement of phi_3 with Dalitz plot analysis of B+ -> D(*)K(*)+ decay

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    We present a measurement of the unitarity triangle angle phi_3 using a Dalitz plot analysis of the K0_S pi+ pi- decay of the neutral D meson from the B+- -> D(*)K(*)+- process. The method employs the interference between D0 and D0bar to extract the angle phi_3, strong phase Delta and the ratio r of suppressed and allowed amplitudes. We apply this method to a 357 fb-1 data sample collected by the Belle experiment. The analysis uses three modes: B+ -> DK+, B+ -> D*K+ with D* -> Dpi0, and B+ -> DK*+ with K*+ -> K0_S pi+, as well as the corresponding charge-conjugate modes. From a combined maximum likelihood fit to the three modes, we obtain phi_3=53+15-18(stat)+-3(syst)+-9(model) degrees. The corresponding two standard deviation interval is 8<phi_3<111 degrees.Comment: 18 pages, 6 figures, 7 tables. To be submitted to Phys. Rev.

    Measurement of Inclusive Radiative B-meson Decays with a Photon Energy Threshold of 1.7 GeV

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    Using 605/fb of data collected at the Upsilon(4S) resonance we present a measurement of the inclusive radiative B-meson decay channel, B to X_s gamma. For the lower photon energy thresholds of 1.7, 1.8, 1.9 and 2.0GeV, as defined in the rest frame of the B-meson, we measure the partial branching fraction and the mean and variance of the photon energy spectrum. At the 1.7GeV threshold we obtain the partial branching fraction BF(B to X_s gamma) = (3.45 +/- 0.15 +/- 0.40) x 10^-4, where the errors are statistical and systematic.Comment: 9 pages, 3 figures, 2 table

    Time-Dependent CP Asymmetries in B0 -> Ks pi0 gamma transitions

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    We report measurements of CP violation parameters in B0->Ks pi0 gamma transitions based on a data sample of 535x10^6 BB pairs collected with the Belle detector at the KEKB asymmetric-energy e+ e- collider. One neutral B meson is fully reconstructed in the B0->Ks pi0 gamma mode. The flavor of the accompanying B meson is identified from its decay products. For a Ks pi0 invariant mass up to 1.8 GeV/c^2, we obtain S = -0.10 +- 0.31 +- 0.07 and A = -0.20 +- 0.20 +- 0.06. For a Ks pi0 invariant mass near the K*0(892) resonance, we obtain S = -0.32 +0.36-0.33 +-0.05 and A=-0.20 +-0.24 +-0.05.Comment: 6 pages, 3 figures, accepted by PR

    Observation of the ϕ(1680)\phi(1680) and the Y(2175) in e+eϕπ+πe^+ e^- \to \phi\pi^+\pi^-

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    The cross sections for e+eϕπ+πe^+ e^- \to \phi\pi^+\pi^- and e^+ e^- \to \phi \fzero are measured from threshold to s=3.0\sqrt{s}=3.0 GeV\hbox{GeV} using initial state radiation. The analysis is based on a data sample of 673 fb1^{-1} collected on and below the Υ(4S)\Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+ee^+e^- collider. First measurements are reported for the resonance parameters of the ϕ(1680)\phi(1680) in the ϕπ+π\phi\pi^+\pi^- mode: m=(1689±7±10)m=(1689\pm 7\pm 10) MeV/c2c^2 and Γ=(211±14±19)\Gamma=(211\pm 14\pm 19) MeV/c2c^2. A structure at s=2.1GeV/c2\sqrt{s}=2.1 \hbox{GeV}/c^2, corresponding to the so called Y(2175), is observed; its mass and width are determined to be 2079±1328+792079\pm13^{+79}_{-28} MeV/c2c^2 and 192±2361+25MeV/c2192\pm23^{+25}_{-61} \hbox{MeV}/c^2, respectively.Comment: 11 pages, 6 figures. Add one plot. Accepted by Phys.Rev.D(RC

    Moments of the Hadronic Invariant Mass Spectrum in B --> X_c l nu Decays at Belle

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    We present a measurement of the hadronic invariant mass squared (M^2_X) spectrum in charmed semileptonic B meson decays B --> X_c l nu based on 140 fb^-1 of Belle data collected near the Y(4S) resonance. We determine the first, the second central and the second non-central moments of this spectrum for lepton energy thresholds ranging between 0.7 and 1.9 GeV. Full correlations between these measurements are evaluated.Comment: published version of the paper (one figure added, minor changes in the text); 16 pages, 3 figures, 10 table
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