25,618 research outputs found

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

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    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

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

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    We report measurements of the differential q2q^2 spectrum and the forward-backward asymmetry for B→K(∗)ℓ+ℓ−B \to K^{(*)} \ell^+\ell^-, where ℓ\ell represents an electron or a muon, with a data sample of 253 fb−1^{-1} accumulated on the Υ(4S)\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

    Studies of B0→ρ±π∓B^0 \to \rho^\pm \pi^\mp and Evidence of B0→ρ0π0B^0 \to \rho^0 \pi^0

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    We report studies of B0→π+π−π0B^0 \to \pi^+ \pi^- \pi^0, using 78fb−178 {\rm fb}^{-1} of data collected at the Υ(4S)\Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric e+e−e^+e^- storage ring. We measure the branching fraction for B0→ρ±π∓B^0 \to \rho^\pm \pi^\mp to be B(B0→ρ±π∓)=(29.1−4.9+5.0(stat)±4.0(syst))×10−6{\mathcal B}(B^0 \to \rho^\pm \pi^\mp) = (29.1 ^{+5.0}_{-4.9}({\rm stat}) \pm 4.0({\rm syst})) \times 10^{-6}, and find an untagged charge asymmetry A=−0.38−0.21+0.19(stat)−0.05+0.04(syst){\mathcal A} = -0.38^{+0.19}_{-0.21} ({\rm stat}) ^{+0.04}_{-0.05} ({\rm syst}). We find the first evidence for B0→ρ0π0B^0 \to \rho^0 \pi^0 with 3.1σ3.1\sigma statistical significance and with a branching fraction of B(B0→ρ0π0)=(6.0−2.3+2.9(stat)±1.2(syst))×10−6{\mathcal B}(B^0 \to \rho^0\pi^0) = (6.0 ^{+2.9}_{-2.3} ({\rm stat}) \pm 1.2 ({\rm syst})) \times 10^{-6}.Comment: Submitted to International Europhysics Conference on High Energy Physics, July 2003, Aachen, German

    Search for the b --> d gamma process

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    We report search results for the flavor-changing neutral current process b --> d gamma with a data sample containing 274 million B meson pairs accumulated at the Upsilon(4S) resonance with the Belle detector at KEKB. We studied the exclusive decays B- --> rho- gamma, B0bar --> rho0 gamma, and B0bar --> omega gamma, and find no significant signal. We set an upper limit for a combined branching fraction Br(B --> (rho,omega) gamma) < 1.4 x 10-6 at the 90% confidence level, which is normalized to that of B- --> rho- gamma assuming an isospin relation between the three modes.Comment: 10 pages, 2 figures, submitted to ICHEP2004, Beijing, Chin

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

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    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

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

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    We report a search for the flavor-changing neutral current decay B→Xsℓ+ℓ−B \to X_{s} \ell^{+} \ell^{-} using a 29.5 fb−1^{-1} data sample accumulated at the Υ(4S)\Upsilon(4S) resonance with the Belle detector at the KEKB e+e−e^{+}e^{-} storage ring. We observe evidence for B→Kμ+μ−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, B(B→Ke+e−)<1.2×10−6{\cal B}(B \to K e^{+} e^{-}) < 1.2 \times 10^{-6}, B(B→K∗(892)e+e−)<5.1×10−6{\cal B}(B \to K^*(892) e^{+} e^{-}) < 5.1 \times 10^{-6}, B(B→K∗(892)μ+μ−)<3.0×10−6{\cal B}(B \to K^*(892) \mu^{+} \mu^{-}) < 3.0 \times 10^{-6}, B(B→Xse+e−)<10.1×10−6{\cal B}(B \to X_{s} e^{+} e^{-}) < 10.1 \times 10^{-6}, B(B→Xsμ+μ−)<19.1×10−6{\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

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    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

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

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    We report the first observation of B0→Ds+π−B^0 \to D_s^+ \pi^- and an improved measurement of Bˉ0→Ds+K−{\bar B^0} \to D_s^+K^- based on 274×106274 \times 10^6 BBˉB{\bar B} events collected with the Belle detector at KEKB. We measure the branching fractions B(Bˉ0→Ds+K−)=(2.93±0.55±0.79)×10−5{\cal B}({\bar B^0} \to D_s^+K^-) = (2.93 \pm 0.55 \pm 0.79) \times 10^{-5} and B(B0→Ds+π−)=(1.94±0.47±0.52)×10−5{\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

    Observation of Radiative B Meson Decays into Higher Kaonic Resonances

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    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^{-1} recorded at the Υ(4S)\Upsilon(4S) resonance with the Belle detector at KEKB. For the two-body final state, we extract the B→K2∗(1430)0γB \to K_2^{*}(1430)^0 \gamma component from an analysis of the helicity angle distribution, and obtain B(B0→K2∗(1430)0γ)=(1.26±0.66±0.10)×10−5{\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→KππγB \to K\pi\pi\gamma signal that is consistent with a mixture of B→K∗πγB \to K^* \pi \gamma and B→KργB \to K \rho \gamma. This is the first time that B→K∗πγB \to K^* \pi \gamma and B→KργB \to K \rho \gamma have been observed separately. We find their branching fractions to be B(B→K∗πγ;MK∗π<2.0GeV/c2)=(5.6±1.1±0.9)×10−5{\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 B(B→Kργ;MKρ<2.0GeV/c2)=(6.5±1.71.2+1.1)×10−5{\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)

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    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
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