New Measurements of Time-Dependent CP-Violating Asymmetries in b --> s Transitions at Belle

We present new measurements of CP-violation parameters in B0 --> phi K0, K+ K- Ks, f0(980) Ks, eta' Ks, omega Ks, Ks pi0, and K*0 gamma (K*0 --> Ks pi0) decays based on a sample of 275 x 10^6 BBbar pairs 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 decay modes are obtained from the asymmetries in the distributions of the proper-time intervals between the two B decays. All results are preliminary.Comment: 23 pages, 3 figures, submitted to ICHEP2004, Beijing, Chin

Evidence for the Electroweak Penguin Decay B→Xsℓ+ℓ−B \to X_{s}\ell^{+}\ell^{-}}

We report a search for the flavor-changing neutral current decay $B \to X_{s} \ell^{+} \ell^{-}$ using a 29.5 fb$^{-1}$ data sample accumulated at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^{+}e^{-}$ storage ring. We observe evidence for $B\to K\mu^+\mu^-$ and report the preliminary branching fraction of {\cal B}(B \to K \mu^{+} \mu^{-}) = (0.99^{+0.39}_{-0.32}^{+0.13}_{-0.15}) \times 10^{-6}. We also set the following 90% confidence level upper limits on the branching fractions for exclusive and inclusive decays, ${\cal B}(B \to K e^{+} e^{-}) < 1.2 \times 10^{-6}$, ${\cal B}(B \to K^*(892) e^{+} e^{-}) < 5.1 \times 10^{-6}$, ${\cal B}(B \to K^*(892) \mu^{+} \mu^{-}) < 3.0 \times 10^{-6}$, ${\cal B}(B \to X_{s} e^{+} e^{-}) < 10.1 \times 10^{-6}$, ${\cal B}(B \to X_{s} \mu^{+} \mu^{-}) < 19.1 \times 10^{-6}$.Comment: Paper submitted to the 2001 Lepton Photon Conferenc

Search for B -> tau nu and B -> K nu nubar Decays with a Fully Reconstructed B at Belle

We present a search for the decays B -> tau nu and B -> K nu nubar in a 253 fb^-1 data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy B factory. Combinatorial and continuum backgrounds are suppressed by selecting a sample of events with one fully reconstructed B. The decay products of the B on the other side of the event are analyzed to search for B -> tau nu and B -> K nu nubar decays. We find no significant evidence for a signal and set 90% confidence level upper limits of B(B -> tau nu) K nu nubar) < 3.6*10^-5.Comment: 12 pages, 6 figures, submitted to the Lepton Photon 2005 conference in Uppsala, Sweden and to the HEP2005 Europhysics Conference in Lisbon, Portuga

A measurement of the rate of wrong-sign decays D0 -> K+ pi-

A D0 meson can decay to K+ pi- through doubly Cabibbo-suppressed decay or via D0-D0bar mixing. With 46.2 fb^{-1} of integrated luminosity collected by Belle, we have measured the time integrated rate of the wrong-sign process D0 -> K+ pi- relative to that of the Cabibbo-favored process D0 -> K- pi+ to be R_WS = (0.372 +- 0.025 +0.009/-0.014) % (preliminary). The D0-D0bar mixing parameters can be derived from the time distribution of the wrong-sign process.Comment: Contributed to ICHEP2002/Amsterda

Observation of Radiative B Meson Decays into Higher Kaonic Resonances

We have studied radiative B meson decays into higher kaonic resonances decaying into a two-body or three-body final state, using a data sample of 21.3 fb$^{-1}$ recorded at the $\Upsilon(4S)$ resonance with the Belle detector at KEKB. For the two-body final state, we extract the $B \to K_2^{*}(1430)^0 \gamma$ component from an analysis of the helicity angle distribution, and obtain ${\cal B}(B^0 \to K_2^{*}(1430)^0 \gamma) = (1.26\pm 0.66\pm 0.10)\times 10^{-5}$. For the three-body final state, we observe a $B \to K\pi\pi\gamma$ signal that is consistent with a mixture of $B \to K^* \pi \gamma$ and $B \to K \rho \gamma$. This is the first time that $B \to K^* \pi \gamma$ and $B \to K \rho \gamma$ have been observed separately. We find their branching fractions to be ${\cal B}(B \to K^* \pi \gamma; M_{K^*\pi}<2.0 GeV/c^2) = (5.6\pm 1.1\pm 0.9)\times 10^{-5}$ and ${\cal B}(B \to K \rho \gamma; M_{K\rho} < 2.0 GeV/c^2) = (6.5\pm 1.7^{+1.1}_{1.2})\times 10^{-5}$, respectively.Comment: Paper submitted to the 2001 Lepton Photon Conferenc

Measurement of the ratio Br(D0 --> pi+pi-pi0)/Br(D0 --> K-pi+pi0)

We report a high-statistics measurement of the relative branching fraction Br(D0 --> pi+pi-pi0)/Br(D0 --> K-pi+pi0). A 357 inverse fb data sample collected with the Belle detector at the KEKB asymmetric-energy e+e- collider was used for the analysis. The relative branching fraction Br(D0 --> pi+pi-pi0)/Br(D0 --> K-pi+pi0) is determined with an accuracy comparable to the latest world average value.Comment: 13 pages, 10 figures, presented at the ICHEP06 Conference, Moscow, Russia, a few typos correcte

Improved Measurements of Direct CP Violation in B --> K+pi-, K+pi0 and pi+pi0 Decays

We report an improved measurement of direct CP violation in the decay B0 --> K+pi-, and a search for CP violation in the decays B+ --> K+pi0 and B+ --> pi+pi0. The measured CP violating asymmetries are Acp(K+pi-)=-0.113+-0.022(stat.)+-0.008(syst.), Acp(K+pi0)=0.04+-0.04(stat.)+-0.02(syst.) and Acp(pi+pi0)=0.02+-0.08(stat.)+-0.01(syst.), where the latter correspond to the intervals -0.03<Acp(K+pi0)<0.11 and -0.12<Acp(pi+pi0)<0.15 at 90% confidence level. These results are obtained from a data sample that contains 386 million BBbar pairs that was collected near the Y(4S) resonance, with the Belle detector at the KEKB asymmetric nergy e+e- collider. All of the results are preliminary.Comment: 11 pages, 3 figures, submitted to the Lepton-Photon 2005 Conference in Uppsala, Sweden and HEP2005 Europhysics Conference in Lisboa, Portuga

Observation of B0→Ds+π−B^0 \to D_s^+ \pi^-

We report the first observation of $B^0 \to D_s^+ \pi^-$ and an improved measurement of ${\bar B^0} \to D_s^+K^-$ based on $274 \times 10^6$ $B{\bar B}$ events collected with the Belle detector at KEKB. We measure the branching fractions ${\cal B}({\bar B^0} \to D_s^+K^-) = (2.93 \pm 0.55 \pm 0.79) \times 10^{-5}$ and ${\cal B}(B^0 \to D_s^+ \pi^-) = (1.94 \pm 0.47 \pm 0.52) \times 10^{-5}$.Comment: 9 pages, 3 figures, submitted to ICHEP2004, Beijing, Chin

Measurement of the Differential q2q^2 Spectrum and Forward-Backward Asymmetry for B→K(∗)ℓ+ℓ−B \to K^{(*)} \ell^+ \ell^-

We report measurements of the differential $q^2$ spectrum and the forward-backward asymmetry for $B \to K^{(*)} \ell^+\ell^-$, where $\ell$ represents an electron or a muon, with a data sample of 253 fb$^{-1}$ accumulated on the $\Upsilon(4S)$ resonance with the Belle detector at KEKB. We also present measurements of the branching fractions and their ratios.Comment: BELLE-CONF-0415, submitted to FPCP04, Daegu, Korea and ICHEP04, Beijing, Chin

Improved Measurements of Bˉ0→D0Kˉ0\bar{B}^0 \to D^0 \bar{K}^0 and Bˉ0→D0Kˉ∗0\bar{B}^0 \to D^0 \bar{K}^{*0} Branching Fractions

We report on an improved study of $\bar{B}^0 \to D^{(*)0} \bar{K}^{(*)0}$ decays, based on $274 \times 10^6$ $B{\bar B}$ events collected with the Belle detector at KEKB. The following branching fractions have been measured: ${\cal B}(\bar{B}^0 \to D^0 \bar{K}^0) = (3.72 \pm 0.65 \pm 0.37) \times 10^{-5}$ and ${\cal B}(\bar{B}^0 \to D^0 \bar{K}^{*0}) = (3.08 \pm 0.56 \pm 0.31) \times 10^{-5}$. We also obtain evidence with $3.2\sigma$ significance for $\bar{B}^0 \to D^{*0} \bar{K}^0$ with ${\cal B}(\bar{B}^0 \to D^{*0} \bar{K}^0) = (3.2^{+1.2}_{-1.1} \pm 0.4) \times 10^{-5}$. No significant signal has been found for the $\bar{B}^0 \to D^{*0} \bar{K}^{*0}$ and $\bar{B}^0 \to \bar{D}^{(*)0} \bar{K}^{*0}$ decay modes, and upper limits at 90% CL are presented.Comment: 9 pages, 3 figures, submitted to ICHEP2004, Beijing, Chin