We study the decay $bar{B}^{0}rightarrowLambda_{c}^{+}bar{p}pi^{+}pi^{-}$, reconstructing the Lambda_{c}^{+} baryon in the $p K^{-}pi^{+}$ mode, using a data sample of $467times 10^{6}$ $Bbar{B}$ pairs collected with the BaBar detector at the PEP-2 s
torage rings at SLAC. We measure branching fractions for decays with intermediate $Sigma_{c}$ baryons to be ${cal B}[bar{B}^{0}rightarrowSigma_{c}(2455)^{++}bar{p}pi^{-}]=(21.3 pm 1.0 pm 1.0 pm 5.5) times 10^{-5}$, ${cal B}[bar{B}^{0}rightarrowSigma_{c}(2520)^{++}bar{p}pi^{-}]=(11.5pm 1.0 pm 0.5 pm 3.0)times 10^{-5}$, ${cal B}[bar{B}^{0}rightarrowSigma_{c}(2455)^{0}bar{p}pi^{+}]=(9.1 pm 0.7 pm 0.4 pm 2.4)times10^{-5}$, and ${cal B}[bar{B}^{0}rightarrowSigma_{c}(2520)^{0}bar{p}pi^{+}]= (2.2 pm 0.7 pm 0.1pm 0.6) times 10^{-5}$, where the uncertainties are statistical, systematic, and due to the uncertainty on the $Lambda_{c}^{+}rightarrowprotonKmpi^{+}$ branching fraction, respectively. For decays without $Sigma_{c}(2455)$ or $Sigma_{c}(2520)$ resonances, we measure ${cal B}[bar{B}^{0}rightarrowLambda_{c}^{+}bar{p}pi^{+}pi^{-}]_{mathrm{non-Sigma_{c}}}=(79 pm 4 pm 4 pm 20)times10^{-5}$. The total branching fraction is determined to be ${cal B}[bar{B}^{0}rightarrowLambda_{c}^{+}bar{p}pi^{+}pi^{-}]_{mathrm{total}}=(123 pm 5 pm 7 pm 32)times10^{-5}$. We examine multibody mass combinations in the resonant three-particle $Sigma_{c}bar{p}pi$ final states and in the four-particle $Lambda_{c}^{+}bar{p}pi^{+}pi^{-}$ final state, and observe different characteristics for the $bar{p}pi$ combination in neutral versus doubly-charged $Sigma_{c}$ decays.
We report on a search for direct CP asymmetry in the singly Cabibbo-suppressed decay D+- --> K+ K- pi+- using a data sample of 476 fb-1 accumulated with the BaBar detector running at and just below the Y(4S) resonance. The CP-violating decay rate asy
mmetry A_CP is determined to be (0.35 +- 0.30 +- 0.15)%. Model-dependent and model-independent Dalitz plot analysis techniques are used to search for CP-violating asymmetries in the various intermediate states.
We report the results of a study of the exclusive charmless semileptonic decays, B^0 --> pi^- l^+ nu, B^+ --> pi^0 l^+ nu, B^+ --> omega l^+ nu, B^+ --> eta l^+ nu and B^+ --> eta^ l^+ nu, (l = e or mu) undertaken with approximately 462x10^6 Bbar{B}
pairs collected at the Upsilon(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions in several bins of q^2, the square of the momentum transferred to the lepton-neutrino pair, for B^0 --> pi^- l^+ nu, B^+ --> pi^0 l^+ nu, B^+ --> omega l^+ nu and B^+ --> eta l^+ nu. From these distributions, we extract the form-factor shapes f_+(q^2) and the total branching fractions BF(B^0 --> pi^- l^+ nu) = (1.45 +/- 0.04_{stat} +/- 0.06_{syst})x10^-4 (combined pi^- and pi^0 decay channels assuming isospin symmetry), BF(B^+ --> omega l^+ nu) = (1.19 +/- 0.16_{stat} +/- 0.09_{syst})x10^-4 and BF(B^+ --> eta l^+ nu) = (0.38 +/- 0.05_{stat} +/- 0.05_{syst})x10^-4. We also measure BF(B^+ --> eta^ l^+ nu) = (0.24 +/- 0.08_{stat} +/- 0.03_{syst})x10^-4. We obtain values for the magnitude of the CKM matrix element V_{ub} by direct comparison with three different QCD calculations in restricted q^2 ranges of B --> pi l^+ nu decays. From a simultaneous fit to the experimental data over the full q^2 range and the FNAL/MILC lattice QCD predictions, we obtain |V_{ub}| = (3.25 +/- 0.31)x10^-3, where the error is the combined experimental and theoretical uncertainty.
Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time reversal violation. The decays of entangled neutral B mesons into definite flavor states ($B^0$ or $bar{B}^0$), and
$J/psi K_S^0$ or $cbar{c} K_S^0$ final states (referred to as $B_+$ or $B_-$), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, $bar{B}^0 rightarrow B_-$ and $B_- rightarrow bar{B}^0$, as a function of the time difference between the two B decays. Using 468 million $Bbar{B}$ pairs produced in $Upsilon(4S)$ decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding $Delta S_T^+ = -1.37 pm 0.14 (stat.) pm 0.06 (syst.)$ and $Delta S_T^- = 1.17 pm 0.18 (stat.) pm 0.11 (syst.)$. These nonzero results represent the first direct observation of T violation through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.
We study the process e+e- -> pi+pi-pi+pi-gamma, with a photon emitted from the initial-state electron or positron, using 454.3 fb^-1 of data collected with the BABAR detector at SLAC, corresponding to approximately 260,000 signal events. We use these
data to extract the non-radiative sigma(e+e- ->pi+pi-pi+pi-) cross section in the energy range from 0.6 to 4.5 Gev. The total uncertainty of the cross section measurement in the peak region is less than 3%, higher in precision than the corresponding results obtained from energy scan data.
We report a measurement of the inclusive semileptonic branching fraction of the B_s meson using data collected with the BaBar detector in the center-of-mass (CM) energy region above the Upsilon(4S) resonance. We use the inclusive yield of phi mesons
and the phi yield in association with a high-momentum lepton to perform a simultaneous measurement of the semileptonic branching fraction and the production rate of B_s mesons relative to all B mesons as a function of CM energy. The inclusive semileptonic branching fraction of the B_s meson is determined to be B(B_s to l nu X)=9.5 (+2.5/-2.0)(stat)(+1.1/-1.9)(syst)%, where l indicates the average of e and mu.
We search for hadronic decays of a light Higgs boson (A0) produced in radiative decays of an Upsilon(2S) or Upsilon(3S) meson, Upsilon --> gamma A0. The data have been recorded by the BABAR experiment at the Upsilon(3S) and Upsilon(2S) center of mass
energies, and include (121.3 pm 1.2) x 10^6 Upsilon(3S) and (98.3 pm 0.9) x 10^6 Upsilon(2S) mesons. No significant signal is observed. We set 90% confidence level upper limits on the product branching fractions B(Upsilon(nS)-->gamma A0) x B(A0-->hadrons) (n=2 or 3) that range from 1 x 10^{-6} for an A0 mass of 0.3 GeV/c^2 to 8 x 10^{-5} at 7 GeV/c^2.
