We measure the branching fraction, polarization and CP asymmetry of B+ -> rho+rho0 decays and search for the decay B+ -> rho+f_0(980) based on a data sample of 231.8 million Y(4S)->BB decays ...collected with the BaBar detector at the SLAC PEP-II asymmetric-energy B factory. In B+ -> rho+rho0 decays we measure B=(16.8+-2.2+-2.3)x10-6, f_L=0.905+-0.042+0.023-0.027, and A_CP=-0.12+-0.13+-0.10, and find an upper limit on the branching fraction of B+ -> rho+f_0(980)(->pi+pi-) of 1.9x10-6 at 90% Confidence Level.
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We report searches for B-meson decays to the charmless final states rho K* and f0(980) K* with a sample of 232 million BBbar pairs collected with the BABAR detector at the PEP-II asymmetric-energy ...e+e- collider at SLAC. We measure the following branching fractions in units of 10^{-6}: B (B+ --> rho0 K*+) = 3.6 +/- 1.7 +/- 0.8 (< 6.1), B (B+ --> rho+ K*0) = 9.6 +/- 1.7 +/- 1.5, B (B0 --> rho- K*+) = 5.4 +/- 3.6 +/- 1.6 (< 12.0), B (B0 --> rho0 K*0) = 5.6 +/- 0.9 +/- 1.3, B (B+ --> f0(980) K*+) = 5.2 +/- 1.2 +/- 0.5, and B (B0 --> f0(980) K*0) = 2.6 +/- 0.6 +/- 0.9 (< 4.3). The first error quoted is statistical, the second systematic, and the upper limits, in parentheses, are given at the 90% confidence level. For the statistically significant modes we also measure the fraction of longitudinal polarization and the charge asymmetry: f_L (B+ --> rho+ K*0) = 0.52 +/- 0.10 +/- 0.04, f_L (B0 --> rho0 K*0) = 0.57 +/- 0.09 +/- 0.08, A_CP (B+ --> rho+ K*0) = -0.01 +/- 0.16 +/- 0.02, A_CP (B0 --> rho0 K*0) = 0.09 +/- 0.19 +/- 0.02, A_CP (B+ --> f_0(980) K*+) = -0.34 +/- 0.21 +/- 0.03, and A_CP (B0 --> f_0(980) K*0) = -0.17 +/- 0.28 +/- 0.02.
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We report observations of the b --> d penguin-dominated decays B+ --> K0bar K+ and B0 --> K0 K0bar in approximately 350 million Upsilon(4S) --> BBbar decays collected with the BaBar detector. We ...measure the branching fractions B(B+ --> K0bar K+) = (1.61 +/- 0.44 +/- 0.09) * 10^-6 and B(B0 --> K0 K0bar) = (1.08 +/- 0.28 +/- 0.11) * 10^-6, and the CP-violating charge asymmetry A_{CP}(K0bar K+) = 0.10 +/- 0.26 +/- 0.03. Using a vertexing technique previously employed in several analyses of all-neutral final states containing kaons, we report the first measurement of time-dependent CP-violating asymmetries in B0 --> K0 K0bar, obtaining S = -1.28 +0.80/-0.73 +0.11/-0.16 and C = -0.40 +/- 0.41 +/- 0.06. We also report improved measurements of the branching fraction B(B+ --> K0 pi+) = (23.9 +/- 1.1 +/- 1.0) * 10^-6 and CP-violating charge asymmetry A_{CP}(K0 pi+) = -0.029 +/- 0.039 +/- 0.010.
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We present a search for D0--anti-D0 mixing using regions of phase space in which the rate of doubly Cabibbo-suppressed decays D0 --> K+ pi- pi0 relative to Cabibbo-favored decays D0 --> K- pi+ pi0 is ...reduced. We analyze 230.4 fb-1 of data collected with the BaBar detector at the PEP-II e+ e- collider at SLAC. We present results with and without the assumption of CP conservation. Assuming CP conservation, we measure the time-integrated mixing rate R_M = (0.023 +0.018/-0.014(stat.) +/- 0.004(syst.))%, and R_M < 0.054% at the 95% confidence level. We find that the data are consistent with no mixing at the 4.5% confidence level. Considering the entire allowed phase space, we measure the branching ratio for D0 --> K+ pi- pi0 relative to D0 --> K- pi+ pi0 to be (0.214 +/- 0.008(stat.) +/- 0.008(syst.))%.
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We report a measurement of the B -> pi l nu branching fraction based on 211 fb-1 of data collected with the BABAR detector. We use samples of B0 and B+ mesons tagged by a second B meson reconstructed ...in a semileptonic or hadronic decay, and combine the results assuming isospin symmetry to obtain BF(B0 -> pi- l+ nu) = (1.33 +/- 0.17(stat) +/- 0.11(syst)) x 10^-4. We determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |Vub| by combining the partial branching fractions measured in ranges of the momentum transfer squared and theoretical calculations of the form factor. Using a recent lattice QCD calculation, we find |Vub| = (4.5 +/- 0.5(stat) +/- 0.3(syst) +0.7/-0.5(FF)) x 10^-3, where the last error is due to the normalization of the form factor.
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Using 226 million $\Upsilon(4S)\to B\bar{B}$ events collected with the BaBar detector at the PEP-II $e^+e^-$ storage ring at the Stanford Linear Accelerator Center, we measure the branching fraction ...for $B^0\to \bar{D}^0 K^+\pi^-$, excluding $B^0\to D^{*-} K^+$ to be $ {\cal B}(B^0\to \bar{D}^0 K^+\pi^-) = (88 \pm 15 \pm 9)\times 10^{-6} . $ We observe $B^0\to \bar{D}^0 K^*(892)^0$ and $B^0\to D_2^*(2460)^- K^+$ contributions. The ratio of branching fractions ${\cal B}(B^0\to D^{*-}K^+)/{\cal B}(B^0\to D^{*-}\pi^+) = (7.76\pm 0.34 \pm 0.29)%$ is measured separately. The branching fraction for the suppressed mode $B^0\to D^0 K^+\pi^-$ is $ {\cal B}(B^0\to D^0 K^+\pi^-) < 19 \times 10^{-6} $ at the 90% confidence level.
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We report the first observation of $e^+e^-$ annihilations into states of positive $C$-parity, namely $\rho^0 \rho^0$ and $\phi\rho^0$. The two states are observed in the $\pip\pim\pip\pim$ and ...$K^+K^-\pip\pim$ final states, respectively, in a data sample of 225~$fb^{-1}$ collected by the $BaBar$~experiment at the $PEP-II$ $e^+e^-$ storage rings at energies near $\sqrt{s} ~=$ 10.58~$GeV$. The distributions of $\cos\theta^*$, where $\theta^*$ is the center-of-mass polar angle of the $\phi$ meson or the forward $\rho^0$ meson, suggest production by two-virtual-photon annihilation. We measure cross sections within the range $|\cos\theta^*| ~<~ 0.8$ of $\sigma(\e^+e^- \to \rho^0 \rho^0) ~=~$$20.7 \pm 0.7 (\mathrm{stat})\pm 2.7(\mathrm{syst}) ~\mathrm{fb}$ and $\sigma(\e^+e^- \to \phi \rho^0) \~=~$$5.7\pm 0.5(\mathrm{stat}) \pm 0.8(\mathrm{syst}) ~\mathrm{fb}$.
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A measurement of the spin of the Omega^- hyperon produced through the exclusive process Xi_c^0 --> Omega^- K^+ is presented using a total integrated luminosity of 116 fb^-1 recorded with the BABAR ...detector at the e^+ e^- asymmetric-energy B-Factory at SLAC. Under the assumption that the Xi_c^0 has spin 1/2, the angular distribution of the Lambda from Omega^- --> Lambda K^- decay is inconsistent with all half-integer Omega^- spin values other than 3/2. Lower statistics data for the process Omega_c^0 --> Omega^- pi^+ from a 230 fb^-1 sample are also found to be consistent with Omega^- spin 3/2. If the Xi_c^0 spin were 3/2, an Omega^- spin of 5/2 cannot be excluded.
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Based on a sample of 227 × 10 6 B ¯¯¯ B pairs collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, we measure the branching fraction B ( B 0 → π 0 π 0 ) = ( 1.17 ± 0.32 ...± 0.10 ) × 10 − 6 , and the asymmetry C π 0 π 0 = − 0.12 ± 0.56 ± 0.06 . The B 0 → π 0 π 0 signal has a significance of 5.0 σ . We also measure B ( B + → π + π 0 ) = ( 5.8 ± 0.6 ± 0.4 ) × 10 − 6 , B ( B + → K + π 0 ) = ( 12.0 ± 0.7 ± 0.6 ) × 10 − 6 , and the charge asymmetries A π + π 0 = − 0.01 ± 0.10 ± 0.02 and A K + π 0 = 0.06 ± 0.06 ± 0.01 . Using isospin relations, we find an upper bound on the angle difference | α − α eff | of 35° at the 90% C.L.
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We present an updated measurement of time-dependent C P asymmetries and the C P -odd fraction in the decay B 0 → D * + D * − using 232 × 10 6 B ¯¯¯ B pairs collected by the BABAR detector at the SLAC ...PEP-II B factory. We determine the C P -odd fraction to be 0.125 ± 0.044 ( stat ) ± 0.007 ( syst ) . The time-dependent C P asymmetry parameters C + and S + are determined to be 0.06 ± 0.17 ( stat ) ± 0.03 ( syst ) and − 0.75 ± 0.25 ( stat ) ± 0.03 ( syst ) , respectively. The standard model predicts these parameters to be 0 and − sin 2 β , respectively, in the absence of penguin amplitude contributions.
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