Measurement of K^+K^- production in two-photon collisions in the resonant-mass region

K^+K^- production in two-photon collisions has been studied using a large data sample of 67 fb^{-1} accumulated with the Belle detector at the KEKB asymmetric e^+e^- collider. We have measured the cross section for the process gamma gamma -> K^+ K^- for center-of-mass energies between 1.4 and 2.4 GeV, and found three new resonant structures in the energy region between 1.6 and 2.4 GeV. The angular differential cross sections have also been measured.Comment: 24 pages, 8 figures, to appear in Euro. Phys. Jour.

Search for the Electric Dipole Moment of the tau Lepton

We have searched for a CP violation signature arising from an electric dipole moment (d_tau) of the tau lepton in the e+e- -> tau+tau- reaction. Using an optimal observable method and 29.5 fb^{-1} of data collected with the Belle detector at the KEKB collider at sqrt{s} = 10.58 GeV, we find Re(d_tau) = (1.15 +- 1.70) x 10^{-17} ecm and Im(d_tau) = (-0.83 +- 0.86) x 10^{-17} ecm and set the 95% confidence level limits -2.2 < Re(d_tau) < 4.5 (10^{-17}ecm) and -2.5 < Im(d_tau) < 0.8 (10^{-17}ecm).Comment: 15 pages, LaTeX, 21 figures, submitted to Phys. Lett.

Search for neutrinoless decays tau -> 3l

We have searched for neutrinoless tau lepton decays into three charged leptons using an 87.1 fb^{-1} data sample collected with the Belle detector at the KEKB e^+e^- collider. Since the number of signal candidate events is compatible with that expected from the background, we set 90% confidence level upper limits on the branching fractions in the range (1.9-3.5) x 10^{-7} for various decay modes tau -> l l l where l represents e or mu.Comment: 12 pages, 4figure

Observation of the Decays B0->K+pi-pi0 and B0->rho-K+

We report the observation of B^0 decays to the K^+pi^-pi^0 final state using a data sample of 78 fb^-1 collected by the Belle detector at the KEKB e^+e^- collider. With no assumptions about intermediate states in the decay, the branching fraction is measured to be (36.6^{+4.2}_{-4.3}+- 3.0)*10^-6.We also search for B decays to intermediate two-body states with the same K^+pi^-pi^0 final state. Significant B signals are observed in the rho(770)^- K^+ and K^*(892)^+pi^- channels, with branching fractions of (15.1^{+3.4+1.4+2.0}_{-3.3-1.5-2.1})* 10^-6 and (14.8^{+4.6+1.5+2.4}_{-4.4-1.0-0.9})* 10^-6, respectively. The first error is statistical, the second is systematic and the third is due to the largest possible interference. Contributions from other possible two-body states will be discussed. No CP asymmetry is found in the inclusive K^+pi^-pi^0 or rho^-K^+ modes, and we set 90% confidence level bounds on the asymmetry of -0.12<A_{CP}<0.26 and -0.18<A_{CP}<0.64, respectively.Comment: 18 pages, 7 figure

Observation of B+ -> K+ eta gamma

We report measurements of radiative B decays with K eta gamma final states, using a data sample of 253 /fb recorded at the Upsilon(4S) resonance with the Belle detector at the KEKB e+e- storage ring. We observe B+ -> K+ eta gamma for the first time with a branching fraction of (8.4 +- 1.5(stat) +1.2 -0.9(syst)) X 10^{-6} for M(Keta) K0 eta gamma. We also search for B -> K3*(1780) gamma.Comment: 12 pages, 5 figures, accepted by Phys. Lett.

Study of B0ˉ→D(∗)0π+π−\bar{B^{0}} \to D^{(*)0} \pi^+ \pi^- Decays

We report on a study of $\bar{B^{0}} \to D^{(*) 0} \pi^+ \pi^-$ decays using 29.1 fb$^{-1}$ of $e^{+}e^{-}$ annihilation data recorded at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB storage ring. Making no assumptions about the intermediate mechanism, the branching fractions for $\bar{B}^0 \to D^0 \pi^+ \pi^-$ and $\bar{B}^0 \to D^{* 0} \pi^+ \pi^-$ are determined to be $(8.0 \pm 0.6 \pm 1.5) \times 10^{-4}$ and $(6.2 \pm 1.2 \pm 1.8) \times 10^{-4}$ respectively. An analysis of $\bar{B^{0}} \to D^{0} \pi^+ \pi^-$ candidates yields to the first observation of the color-suppressed hadronic decay $\bar{B}^0 \to D^0 \rho^0$ with the branching fraction $(2.9 \pm 1.0 \pm 0.4) \times 10^{-4}$. We measure the ratio of branching fractions ${\mathcal B}(\bar{B^0} \to D^0 \rho^0) / {\mathcal B}(\bar{B^0} \to D^0 \omega)$ = 1.6 $\pm$ 0.8.Comment: 13 pages, LaTex, 4 figures, submitted to Phys. Lett.

Measurement of the Branching Fraction for B->eta' K and Search for B->eta'pi+

We report measurements for two-body charmless B decays with an eta' meson in the final state. Using 11.1X10^6 BBbar pairs collected with the Belle detector, we find BF(B^+ ->eta'K^+)=(79^+12_-11 +-9)x10^-6 and BF(B^0 -> eta'K^0)=(55^+19_-16 +-8)x10^-6, where the first and second errors are statistical and systematic, respectively. No signal is observed in the mode B^+ -> eta' pi^+, and we set a 90% confidence level upper limit of BF(B^+-> eta'pi^+) eta'K^+- decays is investigated and a limit at 90% confidence level of -0.20<Acp<0.32 is obtained.Comment: Submitted to Physics Letters

Observation of Cabibbo-suppressed and W-exchange Lambda_c^+ baryon decays

We present measurements of the Cabibbo-suppressed decays Lambda_c^+ --> Lambda0 K+ and Lambda_c^+ --> Sigma0 K+ (both first observations), Lambda_c^+ --> Sigma+ K+ pi- (seen with large statistics for the first time), Lambda_c^+ --> p K+ K- and Lambda_c^+ --> p phi (measured with improved accuracy). Improved branching ratio measurements for the decays Lambda_c^+ --> Sigma+ K+ K- and Lambda_c^+ --> Sigma+ phi, which are attributed to W-exchange diagrams, are shown. We also present the first evidence for Lambda_c^+ --> Xi(1690)^0 K+ and set an upper limit on the non-resonant decay Lambda_c^+ --> Sigma+ K+ K-. This analysis was performed using 32.6 fb^{-1} of data collected by the Belle detector at the asymmetric e+ e- collider KEKB.Comment: Submitted to Phys. Lett. B. v2: A small correction to the Authorlist was made. An earlier version of this analysis was released as BELLE-CONF-0130, hep-ex/010800

Measurements of Branching Fractions and Decay Amplitudes in B-> J/\psi K^* decays

The branching fractions and the decay amplitudes of B -> J/psi K^* decays are measured in a 29.4/fb data sample collected with the Belle detector at the KEKB electron-positron collider. The decay amplitudes of helicity states of the J/psi K^* system are determined from the full angular distribution of the final state particles in the transversity basis. The branching fractions are measured to be (1.29\pm0.05\pm0.13) \times 10^{-3} for neutral mesons and (1.28\pm0.07\pm0.14) \times 10^{-3} for charged mesons. The measured longitudinal and transverse (perpendicular to the transversity plane) amplitudes are |A_0|^2 = 0.62\pm0.02\pm0.03 and |A_{\perp}|^2 = 0.19\pm0.02\pm0.03, respectively. The value of |A_{\perp}|^2 shows that the CP even component dominates in the B^0 \to J/\psi K^{*0}(K_S\pi^0) decay.Comment: 17 pages, 3 figures, 5 tables, to appear in Phys. Lett.

Measurement of the inclusive semileptonic branching fraction of B mesons and |Vcb|

We present a measurement of the electron spectrum from inclusive semileptonic {\it B} decay, using 5.1 fb$^{-1}$ of $\Upsilon(4S)$ data collected with the Belle detector. A high-momentum lepton tag was used to separate the semileptonic {\it B} decay electrons from secondary decay electrons. We obtained the branching fraction, ${\cal B}(B\to X e^+ \nu) = (10.90 \pm 0.12 \pm 0.49)$, with minimal model dependence. From this measurement, we derive a value for the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}| = 0.0408 \pm 0.0010 {\rm (exp)} \pm 0.0025{\rm (th)}$.Comment: 16 pages, 3 figures, 3 table