231 research outputs found

    Measurement of CP Asymmetries in B0 --> K0S K0S K0S Decays

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    We present measurements of the time-dependent CP-violating asymmetries in B0 --> K0S K0S K0S decays based on 384 million Y(4S) decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We obtain the CP asymmetry parameters C = 0.02 +/- 0.21 +/- 0.05 and S = -0.71 +/- 0.24 +/- 0.04, where the first uncertainties are statistical and the second systematic. These results are consistent with standard model expectations

    Measurement of the Time-Dependent CP Asymmetry in B0 --> D(*)0_CP h0 Decays

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    We report a measurement of the time-dependent CP-asymmetry parameters S\cal S and C\cal C in color-suppressed B0D()0h0B^0 \to D^{(*)0} h^0 decays, where h0h^0 is a π0\pi^0, η\eta, or ω\omega meson, and the D0D^0 decays to one of the CP eigenstates K+KK^+K^-, KSπ0K_S\pi^0, or KSωK_S\omega. The data sample consists of 383×106383\times 10^{6} Υ(4S)BBˉ\Upsilon(4S)\to B\bar{B} decays collected with the BABAR detector at the PEP-II asymmetric-energy BB-factory at SLAC. The results are S=0.56±0.23±0.05{\cal S}= -0.56 \pm 0.23 \pm 0.05 and C=0.23±0.16±0.04{\cal C}= -0.23\pm 0.16\pm 0.04, where the first error is statistical and the second is systematic

    Improved Measurement of CP Violation in Neutral B Decays to c cbar s

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    We present updated measurements of time-dependent CP asymmetries in fully-reconstructed neutral B decays to several CP eigenstates containing a charmonium meson. The measurements use a data sample of (383 +/- 4) x 10^6 Y(4S)-> BBbar decays collected with the BABAR detector at the PEP-II B factory. We determine sin2beta = 0.714 +/- 0.032 (stat) +/- 0.018 (syst) and |lambda| = 0.952 +/- 0.022 (stat) +/- 0.017 (syst)

    Observation of CP Violation in B0 -> K+pi- and B0 -> pi+pi-

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    We report observations of CP violation in the decays B0 -> K+pi- and B0 -> pi+pi- in a sample of 383 million Y4S -> BBbar events. We find 4372 +/- pi+82 B0 -> K+pi- decays and measure the direct CP-violating charge asymmetry -> K+Akpi = -0.107 +/- 0.018 (stat) +0.007-0.004 (syst), which excludes the CP-conserving hypothesis with a significance of 5.5 standard deviations. In the same sample we find 1139 +/- 49 B0 -> pi+pi- decays and measure the CP-violating asymmetries Spipi = -0.60 +/- 0.11 (stat) +/- 0.03 (syst) and Cpipi = -0.21 +/- 0.09 (stat) +/- 0.02 (syst). CP conservation in B0 -> pi+pi- (Spipi=Cpipi=0) is excluded at a confidence level 1-C.L. = 8 * 10^{-8}, corresponding to 5.4 standard deviations

    Measurement of CP-Violating Asymmetries in B0-->(rhopi)0 Using a Time-Dependent Dalitz Plot Analysis

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    We report a measurement of CP-violating asymmetries in B0-->(rhopi)0-->pi+pi-pi0 decays using a time-dependent Dalitz plot analysis. The results are obtained from a data sample of 375 million Y(4S) --> BBbar decays, collected by the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. We measure 26 coefficients of the bilinear form-factor terms occurring in the time-dependent decay rate of the B0 meson. We derive the physically relevant quantities from these coefficients. In particular, we measure a constraint on the angle alpha of the Unitarity Triangle

    Measurements of CP-Violating Asymmetries in B0 to a1(1260)^{+-} pi^{-+} Decays

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    We present measurements of CP-violating asymmetries in the decay B0 -> a_1(1260)^{+-} pi^{-+} with a_1(1260)^{+-} -> pi^{-+} pi^{+-} pi^{+-}. The data sample corresponds to 384 million B B-bar pairs collected with the BaBar detector at the PEP-II asymmetric B-factory at SLAC. We measure the CP-violating asymmetry A^{a_1 \pi}_{CP}=-0.07+-0.07+-0.02, the mixing-induced CP violation parameter S_{a_1 \pi}= 0.37 +-0.21+-0.07, the direct CP violation parameter C_{a_1 \pi}=-0.10+-0.15+-0.09, and the parameters \Delta C_{a_1 \pi}=0.26+-0.15+-0.07 and \Delta S_{a_1\pi}=-0.14+-0.21+-0.06. From these measured quantities we determine the angle \alpha_{\rm eff}= 78.6^{\circ} +- 7.3^{\circ}

    Measurement of the Branching Fraction and Time-Dependent CP Asymmetry in the Decay B0->D*+D*-Ks

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    We study the decay B0->D*+D*-Ks using (230 +/- 2) x 10^{6} BBbar pairs collected by the Babar detector at the PEP-II B factory. We measure a branching fraction B(B0->D*+D*-Ks)=(4.4\pm0.4\pm0.7)\times 10^{-3} and find evidence for the decay B0->D*- D+_{s1}(2536) with a statistical significance of 4.6σ4.6 \sigma. A time-dependent CP asymmetry analysis is also performed to study the possible resonant contributions to B0->D*+D*-Ks and the sign of cos2beta . Our measurement indicates that there is a sizable resonant contribution to the decay B0->D*+D*-Ks from a unknown Ds1+D^+_{s1} state with large width, and that cos2beta is positive at the 94 % confidence level under certain theoretical assumptions

    Search for inclusive charmless B->K+X and B->K0X decays

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    We present preliminary results from a search for inclusive charmless B->KX decays. These decays occur dominantly via one-loop b->s penguin transitions, and can provide useful information about these processes. Using a sample of 288.5/fb collected with the BABAR detector at the PEP-II asymmetric-energy e+e- B Factory at SLAC, we search for high-energy kaons recoiling against fully reconstructed B decays. We measure the partial branching fractions for kaons with momentum p*(K)>2.34GeV in the B rest frame, and obtain (in units of 10^-6): B(B->K+X, p*>2.34GeV) = 196^{+37}_{-34}(stat.)^{+31}_{-30}(syst.) and B(B->K0X, p*>2.34GeV) = 154^{+55}_{-48}(stat.)^{+55}_{-41}(syst.) (<266 at 90% C.L.)

    Search for b--> u transitions in B- -> [K+pi-pi0]_D K-

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    We search for decays of a B meson into a neutral D meson and a kaon, with the D meson decaying into K+pi-pi0. This final state can be reached through the b --> c transition B- -> D0K- followed by the doubly Cabibbo-suppressed D0 --> K+pi-pi0, or the b --> u transition B- --> D0bar K- followed by the Cabibbo-favored D0bar --> K+ pi-pi0. The interference of these two amplitudes is sensitive to the angle gamma of the unitarity triangle. We present preliminary results based on 226 10^{6} e+e- --> Y(4s) --> BBbar events collected with the BABAR detector at SLAC. We find no significant evidence for these decays and we set a limit R_ADS =(BR(B- -->[K+pi-pi0]_D K-)+ BR(B- --> [K-pi+pi0]_D K+))/(BR(B- -->[K-pi+pi0]_D K-)+ BR(B- --> [K+pi-pi0]_D K+)) D0bar K-)|/|A(B- --> D0bar K-)| < 0.185 at 95% confidence level

    Measurement of CP-Violating Asymmetries in the B0->K+K-K0 Dalitz Plot

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    We present a preliminary measurement of CP-violation parameters in the decay B0 -> K+K-K0, using approximately 347 million BBbar events collected by the BABAR detector at SLAC. Reconstructing the neutral kaon as KS -> pi+pi-, KS -> pi0pi0, or KL, we analyze the Dalitz plot distribution and measure fractions to intermediate states. We extract CP parameters from the asymmetries in amplitudes and phases between B0 and B0bar decays across the Dalitz plot. For decays to phiK0, we find beta_eff=0.06 +/- 0.16 +/- 0.05, Acp=-0.18 +/- 0.20 +/- 0.10, where the first uncertainty is statistical and the second one is systematic. For decays to f0K0, we find beta_eff=0.18 +/- 0.19 +/- 0.04, Acp=0.45 +/- 0.28 +/- 0.10. Combining all KKK0 events and taking account of the different CP eigenvalues of the individual Dalitz plot components, we find beta_eff = 0.361 +/- 0.079 +/- 0.037, Acp = -0.034 +/- 0.079 +/- 0.025. The trigonometric reflection at pi/2 - beta_eff is disfavored at 4.6 sigma. We also study angular distributions in B0 -> K+K-KS and B+ -> phi K+ decays and measure the direct CP asymmetry in B+ -> phi K+ decays, Acp = 0.046 +/- 0.046 +/- 0.017
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