4,197 research outputs found

    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

    Measurement of the Branching Fraction of the Decay B+π+π+ν\boldsymbol{B^{+}\to\pi^{+}\pi^{-}\ell^{+}\nu_\ell} in Fully Reconstructed Events at Belle

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    We present an analysis of the exclusive B+π+π+νB^{+}\to\pi^{+}\pi^{-}\ell^{+}\nu_{\ell} decay, where \ell represents an electron or a muon, with the assumption of charge-conjugation symmetry and lepton universality. The analysis uses the full Υ(4S)\Upsilon(4S) data sample collected by the Belle detector, corresponding to 711 fb1^{-1} of integrated luminosity. We select the events by fully reconstructing one BB meson in hadronic decay modes, subsequently determining the properties of the other BB meson. We extract the signal yields using a binned maximum-likelihood fit to the missing-mass squared distribution in bins of the invariant mass of the two pions or the momentum transfer squared. We measure a total branching fraction of B(B+π+π+ν)=[22.71.6+1.9(stat)±3.5(syst)]×105{{\cal B}(B^{+}\to \pi^{+}\pi^{-}\ell^{+}\nu_{\ell})= [22.7 ^{+1.9}_{-1.6} (\mathrm{stat}) \pm 3.5(\mathrm{syst}) ]\times 10^{-5}}, where the uncertainties are statistical and systematic, respectively. This result is the first reported measurement of this decay.Comment: 23 pages, 19 figure

    Measurement Of |V_ub| From Inclusive Charmless Semileptonic B Decays

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    We present the partial branching fraction for inclusive charmless semileptonic B decays and the corresponding value of the CKM matrix element |Vub|, using a multivariate analysis method to access ~90% of the B -> Xu l nu phase space. This approach dramatically reduces the theoretical uncertainties from the b-quark mass and non-perturbative QCD compared to all previous inclusive measurements. The results are based on a sample of 657 million B -Bbar pairs collected with the Belle detector. We find that Delta BR(B -> Xu l nu; p^*B_l>1.0 GeV/c=1.963 x (1 +/- 0.088(stat.) +/- 0.081(sys.)) x 10^-3. Corresponding values of |Vub| are extracted using several theoretical calculations.Comment: 9 pages, 1 figure, 2 tables. Published in PR

    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

    Measurements of Charmless Hadronic b->s Penguin Decays in the pi+pi-K+pi- Final State and First Observation of B0 -> rho0K+pi-

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    We report measurements of charmless hadronic B^0 decays into the pi+pi-K+pi+ final state. The analysis uses a sample of 657x10^6 BBbar pairs collected with the Belle detector at the KEKB asymmetric-energy e+e- collider at the Y(4S) resonance. The decay B^0 -> rho0 Kpi is observed for the first time; the significance is 5.0sigma and the corresponding partial branching fraction for M_Kpi in (0.75,1.20) GeV/c^2 is [2.8 +- 0.5(stat) +-0.5(syst)] x 10^{-6}. We also obtain the first evidence for B^0 -> f0Kpi with 3.5sigma significance and for B^0 -> pi+pi-K*0 with 4.5sigma significance. For the two-body decays B^0 -> rho0K*0 and B^0 -> f0K*0, the significances are 2.7sigma and 2.5sigma, respectively, and the upper limits on the branching fractions are 3.4x10^{-6} and 2.2x10^{-6} at 90% confidence level.Comment: 6 pages, 3 figures. accepted by PRD(RC

    Dalitz analysis of B --> K pi psi' decays and the Z(4430)+

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    From a Dalitz plot analysis of B --> K pi psi' decays, we find a signal for Z(4430)+ --> pi+ psi' with a mass M= (4443(+15-12)(+19-13))MeV/c^2, width Gamma= (107(+86-43)(+74-56))MeV, product branching fraction BR(B0 --> K- Z(4430)+) x BR(Z(4430)+ --> pi+ psi')= (3.2(+1.8-0.9)(+5.3-1.6)) x 10^{-5}, and significance of 6.4sigma that agrees with previous Belle measurements based on the same data sample. In addition, we determine the branching fraction BR(B^0 --> K*(892)^0 psi')= (5.52(+0.35-0.32)(+0.53-0.58)) x 10^{-4} and the fraction of K*(892)^0 mesons that are longitudinally polarized f_L= 44.8(+4.0-2.7)(+4.0-5.3)%. These results are obtained from a 605fb^{-1} data sample that contains 657 million B-anti-B pairs collected near the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider.Comment: Final version published in PRD(RC

    Measurement of the e+e- --> D0D*-pi+ cross section using initial-state radiation

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    We report measurements of the exclusive cross section for e+e- --> D0D*-pi+ as function of center-of-mass energy from the D0D*-pi+ threshold to 5.2 GeV with initial-state radiation. No evidence is found for Y(4260)-->D0D*-pi+ decays. The analysis is based on a data sample collected with the Belle detector at or near a center-of-mass energy of 10.58 GeV with an integrated luminosity of 695 1/fb at the KEKB asymmetric-energy e+e- collider.Comment: 7 pages, 3 figures, presented at EPS09 and LP09 conference

    First Measurement of Inclusive B -> X_s eta Decays

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    We report a first measurement of inclusive B -> X_s eta decays, where X_s is a charmless state with unit strangeness. The measurement is based on a pseudo-inclusive reconstruction technique and uses a sample of 657 x 10^6 BB-bar pairs accumulated with the Belle detector at the KEKB e^+e^- collider. For M_{X_s} < 2.6 GeV/c^2, we measure a branching fraction of (26.1 +/- 3.0 (stat) +1.9 -2.1 (syst) +4.0 -7.1 (model)) x 10^-5 and a direct CP asymmetry of A_{CP} = -0.13 +/- 0.04 +0.02 -0.03. Over half of the signal occurs in the range M_{X_s} > 1.8 GeV/c^2.Comment: 6 pages, 1 figure, 1 table, submitted to Physical Review Letter

    Measurement of CP violating asymmetries in B^0 -> K^+K^- K^0_S decays with a time-dependent Dalitz approach

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    We report a measurement of CPCP violating asymmetries in B0(B0)K+KKS0B^0(\overline{B}^0) \to K^+ K^- K^0_S decays with a time-dependent Dalitz approach. This analysis is based on a data sample of 657×106657\times 10^6 BBB\overline{B} pairs accumulated at the Υ(4S)\Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+ee^+e^- collider. As the result of an unbinned maximum likelihood fit to the selected candidates, the mixing-induced and direct CPCP violation parameters, ϕ1eff\phi^{\rm eff}_1 and ACP{\cal A}_{CP} are obtained for B0ϕ(1020)KS0B^0 \to \phi(1020) K^0_S, B0f0(980)KS0B^0 \to f_0(980) K^0_S and other B0K+KKS0B^0 \to K^+ K^- K^0_S decays. We find four solutions that describe the data. There are \{eqnarray*} \phi_1^{\rm eff}(B^0\to \phi(1020) K^0_S) & = & (32.2 \pm 9.0 \pm 2.6 \pm 1.4)^{\circ}; \phi_1^{\rm eff}(B^0\to \phi(1020) K^0_S) & = & (26.2 \pm 8.8 \pm 2.7 \pm 1.2)^{\circ};\\ \phi_1^{\rm eff}(B^0\to \phi(1020) K^0_S) & = & (27.3 \pm 8.6 \pm 2.8 \pm 1.3)^{\circ}\; {\rm and}\\ \phi_1^{\rm eff}(B^0\to \phi(1020) K^0_S) & = & (24.3 \pm 8.0 \pm 2.9 \pm 5.2)^{\circ}.{eqnarray*}\ The values for the CPCP violating phase in B0ϕ(1020)KS0B^0\to \phi(1020) K^0_S are similar but other properties of the Dalitz plot are quite different for the four solutions. These four solutions have consistent ϕ1eff\phi^{\rm eff}_1 values for all three BB meson decay channels and none of them deviates significantly from the values measured in B(ccˉ)K0B \to (c\bar{c}) K^0 decays with the currently available statistics. In addition, we find no significant direct CPCP violation.Comment: submitted to PR
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