Measurement of Time-Dependent CP-Violating Asymmetries in B0 --> phi Ks0, K+ K- Ks0, and eta' Ks0 Decays

We present an improved measurement of CP-violation parameters in B0 --> phi Ks0, K+ K- Ks0, and eta' Ks0 decays based on a 140 fb-1 data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB energy-asymmetric e+e- collider. One neutral B meson is fully reconstructed in one of the specified decay channels, and the flavor of the accompanying B meson is identified from its decay products. CP-violation parameters for each of the three modes are obtained from the asymmetries in the distributions of the proper-time intervals between the two B decays. We find that the observed CP asymmetry in the B0 --> phi Ks0 decay differs from the standard model (SM) expectation by 3.5 standard deviations, while the other cases are consistent with the SM.Comment: 10 pages, 4 postscript figures, submitted to Physical Review Letters, also contributed to the XXI International Symposium on Lepton and Photon Interactions at High Energies, Aug 11-16, 2003, Fermilab, Illinois US

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

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

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

Evidence for B0->pi0pi0

We report evidence for the decay B0->pi0pi0. The analysis is based on a data sample of 152million BBbar pairs collected at the Upsilon(4s) resonance with the Belle detector at the KEKB e+e- storage ring. We find 25.6+9.3/-8.4(stat)+1.6/-1.4(syst) B0->pi0pi0 signal events with a significance of 3.4 standard deviations. We measure the branching fraction to be (1.7+-0.6(stat)+-0.2(syst))*10^{-6}.Comment: Submitted to PR

Observation of a narrow charmonium-like state in exclusive B+ -> K+ pi+pi- J/psi decays

We report the observation of a narrow charmonium-like state produced in the exclusive decay process B+ -> K+ pi+pi- J/psi. This state, which decays into pi+pi- J/psi, has a mass of 3872.0+-0.6(stat)+-0.5(syst) MeV, a value that is very near the M_D + M_D* mass threshold. The results are based on an analysis of 152M B-Bbar events collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider. The statistical significance of the signal is in excess of 10 sigma.Comment: 10 pages 4 figures, submitted to Physical Review Letter

Observation of B→K∗ℓ+ℓ−B \to K^* \ell^+ \ell^-

We report the first observation of the flavor-changing neutral current decay $B \to K^* \ell^+ \ell^-$ and an improved measurement of the decay $B \to K \ell^+ \ell^-$, where $\ell$ represents an electron or a muon, with a data sample of 140 fb${}^{-1}$ accumulated at the $\Upsilon(4S)$ resonance with the Belle detector at KEKB. The results for the branching fractions are ${\cal B}(B \to K^* \ell^+ \ell^-)=(11.5^{+2.6}_{-2.4} \pm 0.8 \pm 0.2) \times 10^{-7}$ and ${\cal B}(B \to K \ell^+ \ell^-)=(4.8^{+1.0}_{-0.9} \pm 0.3 \pm 0.1) \times 10^{-7}$, where the first error is statistical, the second is systematic and the third is from model dependence.Comment: 11 pages, 2 figures, submitted to PR

Search for the Lepton-Flavor-Violating Decay τ−→μ−η\tau^- \to \mu^- \eta at Belle

We have searched for the Lepton Flavor Violating decay $\tau^- \to \mu^- \eta$ using a data sample of 84.3 fb$^{-1}$ accumulated with the Belle detector at KEK. The $\eta$-meson was detected through the decay modes: $\eta \to \gamma\gamma$ and $\pi^+\pi^-\pi^0$. No signal candidates are found, and we obtain an upper limit for the branching fraction ${\cal B}(\tau^- \to \mu^- \eta)<3.4\times 10^{-7}$ at the 90% confidence level.Comment: Submitted to Phys.Rev.Let

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

Measurement of branching fraction ratios and CP asymmetries in B±→DCPK±B^{\pm} \to D_{CP}K^{\pm}

We report results on the decay $B^{-} \to D_{CP}K^{-}$ and its charge conjugate using a data sample of 85.4 million $B\bar{B}$ pairs recorded at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric $e^{+}e^{-}$ storage ring. Ratios of branching fractions of Cabibbo-suppressed to Cabibbo-favored processes are determined to be ${\cal B}(B^- \to D^0 K^-)/{\cal B}(B^- \to D^0 \pi^-)= 0.077 \pm 0.005(stat) \pm 0.006(sys)$, ${\cal B}(B^- \to D_1 K^-)/{\cal B}(B^- \to D_1 \pi^-) = 0.093 \pm 0.018(stat) \pm 0.008(sys)$ and ${\cal B}(B^- \to D_2 K^-)/{\cal B}(B^- \to D_2 \pi^-) = 0.108 \pm 0.019(stat) \pm 0.007(sys)$ where the indices 1 and 2 represent the CP=+1 and CP=$-$1 eigenstates of the $D^{0}-\bar{D^{0}}$ system, respectively. We find the partial-rate charge asymmetries for $B^{-} \to D_{CP}K^{-}$ to be ${\cal{A}}_1 = 0.06 \pm 0.19(stat) \pm 0.04(sys)$ and ${\cal{A}}_2 = -0.19 \pm 0.17(stat) \pm 0.05(sys)$.Comment: 10 pages, 3 figures, submitted to Physical Review