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.

Observation of Large CP Violation and Evidence for Direct CP Violation in B0-->pi+pi- Decays

We report the first observation of CP-violating asymmetries in B0 --> pi+pi- decays based on a 140 fb-1 data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We reconstruct one neutral B meson as a B0 --> pi+pi- CP eigenstate and identify the flavor of the accompanying B meson from its decay products. We apply an unbinned maximum likelihood fit to the distribution of the time intervals between the two B meson decay points. The fit yields the CP-violating asymmetry amplitudes Apipi = +0.58+/-0.15(stat)+/-0.07(syst) and Spipi = -1.00+/-0.21(stat)+/-0.07(syst). We rule out the CP-conserving case, Apipi=Spipi=0, at a level of 5.2 standard deviations. We also find evidence for direct CP violation with a significance at or greater than 3.2 standard deviations for any Spipi value.Comment: 9 pages, 3 figure

Measurement of the CP Violation Parameter sin(2phi_1) in B^0_d Meson Decays

We present a measurement of the Standard Model CP violation parameter sin(2phi_1) based on a 10.5 fb^{-1} data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric e+e- collider. One neutral B meson is reconstructed in the J/psi K_S, psi(2S) K_S, chi_{c1} K_S, eta_c K_S, J/psi K_L or J/psi pi^0 CP-eigenstate decay channel and the flavor of the accompanying B meson is identified from its charged particle decay products. From the asymmetry in the distribution of the time interval between the two B-meson decay points, we determine sin(2phi_1) = 0.58 +0.32-0.34 (stat) +0.09-0.10 (syst).Comment: LaTex, 13 pages, 3 figures, submitted to P.R.

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.

Observation of Radiative Decay D0→ϕγD^0 \to \phi \gamma

We report the observation of the decay $D^{0} \to \phi \gamma$ with a statistical significance of $5.4\sigma$ in 78.1 \ifb of data collected by the Belle experiment at the KEKB $e^+ e^-$ collider. This is the first observation of a flavor-changing radiative decay of a charmed meson. The Cabibbo- and color-suppressed decays $D^0 \to \phi \pi^0$, $\phi \eta$ 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

An Upper Bound on the Decay tau -> mu gamma from Belle

We have performed a search for the lepton-flavor-violating decay tau -> mu gamma using a data sample of 86.3fb^{-1} accumulated by the Belle detector at KEK. No evidence for a signal is seen, and we set an upper limit for the branching fraction of B(tau -> mu gamma) < 3.1 x 10^{-7} at the 90% confidence level.Comment: 6 pages, 4 figuresm, submitted to Phys. Rev. Let

An inclusive measurement of the photon energy spectrum in b->s gamma decays

We report a fully inclusive measurement of the flavour changing neutral current decay b->s gamma in the energy range 1.8 GeV < E* < 2.8 GeV, covering 95% of the total spectrum. Using 140 fb^-1 we obtain BF(b->s gamma)= 3.55 +/- 0.32 +0.30-0.31 +0.11-0.07, where the errors are statistical, systematic and from theory corrections. We also measure the first and second moments of the photon energy spectrum above 1.8 GeV and obtain = 2.292 +/- 0.026 +/- 0.034 GeV and -^2 = 0.0305 +/- 0.0074 +/- 0.0063 GeV^2, where the errors are statistical and systematic.Comment: RevTex4, 6 pages, Submitted to Phys.Rev.Lett. Replaced: added table of systematic errors. New results take into account radiative J/Psi decay

Improved Measurements of Partial Rate Asymmetry in B -> h h Decays

We report improved measurements of the partial rate asymmetry (Acp) in B -> h h decays with 140fb^-1 of data collected with the Belle detector at the KEKB e+e- collider. Here h stands for a charged or neutral pion or kaon and in total five decay modes are included: K-+ pi+-, K0s pi-+, K-+ pi0, pi-+ pi0 and K0s pi0. The flavor of the last decay mode is determined from the accompanying B meson. Using a data sample 4.7 times larger than that of our previous measurement, we find Acp(K-+ pi+-) -0.088+-0.035+-0.013, 2.4 sigma from zero. Results for other decay modes are also presented.Comment: 9 pages, 1 figur

Measurements of the DsJD_{sJ} resonance properties

We report measurements of the properties of the $D_{sJ}^+(2317)$ and $D_{sJ}^+(2457)$ resonances produced in continuum $e^+ e^-$ annihilation near $\sqrt{s}=10.6 \mathrm{GeV}$. The analysis is based on an $86.9 \mathrm{fb^{-1}}$ data sample collected %at and 60 MeV below the $\Upsilon(4S)$ resonance with with the Belle detector at KEKB. We determine the masses to be $M(D_{sJ}^+(2317)) = 2317.2 \pm 0.5(\mathrm{stat}) \pm 0.9(\mathrm{syst}) \mathrm{MeV}/c^2$ and $M(D_{sJ}^+(2457))=2456.5 \pm 1.3(\mathrm{stat}) \pm 1.3(\mathrm{syst}) \mathrm{MeV}/c^2$. We observe the radiative decay mode $D_{sJ}^+(2457) \to D_s^+ \gamma$ and the dipion decay mode $D_{sJ}^+(2457) \to D_s^+ \pi^+ \pi^-$, and determine their branching fractions. No corresponding decays are observed for the $D_{sJ}(2317)$ state. These results are consistent with the spin-parity assignments of $0^+$ for the $D_{sJ}(2317)$ and $1^+$ for the $D_{sJ}(2457)$.Comment: 5 pages, 6 figures; Added content, updated and paper submitted to PR