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We report a search for CP violation in the decay \tau- -> \pi - \K^0_S (>= 0 \pi 0) \nu_\tau\ using a dataset of 437 million \tau\ lepton pairs, corresponding to an integrated luminosity of 476 fb^{-1}, collected with the BABAR detector at the PEP-II asymmetric energy e+e- storage rings. The CP-violating decay-rate asymmetry is determined to be (-0.45 +/- 0.24 +/- 0.11)%, approximately three standard deviations from the Standard Model prediction of (0.33 +/- 0.01)%.
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.
We present searches for rare or forbidden charm decays of the form $X_c^+\to h^\pm\ell^\mp\ell^{(\prime)+}$, where $X_c^+$ is a charm hadron ($D^+$, $D^+_s$, or $\Lambda_c^+$), $h^\pm$ is a pion, kaon, or proton, and $\ell^{(\prime)\pm}$ is an electron or muon. The analysis is based on $384 fb^{-1}$ of $e^+e^-$ annihilation data collected at or close to the $\Upsilon(4S)$ resonance with the BaBar detector at the SLAC National Accelerator Laboratory. No significant signal is observed for any of the 35 decay modes that are investigated. We establish 90% confidence-level upper limits on the branching fractions between $1 \times 10^{-6}$ and $44 \times 10^{-6}$ depending on the channel. In most cases, these results represent either the first limits or significant improvements on existing limits for the decay modes studied.
Using a sample of 122 million Upsilon(3S) events recorded with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we search for the h_b(1P) spin-singlet partner of the P-wave chi_b(1P) states in the sequential decay Upsilon(3S) --> pi0 h_b(1P), h_b(1P) --> gamma eta_b(1S). We observe an excess of events above background in the distribution of the recoil mass against the pi0 at mass 9902 +/- 4 (stat.) +/- 1 (syst.) MeV/c^2. The width of the observed signal is consistent with experimental resolution, and its significance is 3.0 sigma, including systematic uncertainties. We obtain the value (3.7 +/- 1.1 (stat.) +/- 0.7 (syst.))x 10^{-4} for the product branching fraction BF(Upsilon(3S) --> pi0 h_b) x BF(h_b --> gamma eta_b).
We report the observation of the baryonic B decay B0bar --> Lambda_c^+ anti-Lambda K- with a significance larger than 7 standard deviations based on 471x10^6$ BBbar pairs collected with the BABAR detector at the PEP-II storage ring at SLAC. We measure the branching fraction for the decay B0bar --> Lambda_c^+ anti-Lambda K- to be (3.8 \pm 0.8_{stat} \pm 0.2_{sys} \pm 1.0_{Lambda_c^+})x10^{-5}. The uncertainties are statistical, systematic, and due to the uncertainty in the Lambda_c^+ branching fraction. We find that the Lambda_c^+ K^- invariant mass distribution shows an enhancement above 3.5 GeV/c^2.
We use 111+/-1 million Upsilon(3S) and 89+/-1 million Upsilon(2S) events recorded by the BaBar detector at the PEP-II B-factory at SLAC to perform a study of radiative transitions between bottomonium states using photons that have been converted to e+e- pairs by the detector material. We observe Upsilon(3S) -> gamma chi_b0,2(1P) decay, make precise measurements of the branching fractions for chi_b1,2(1P,2P) -> gamma Upsilon(1S) and chi_b1,2(2P) -> gamma Upsilon(2S) decays, and search for radiative decay to the eta_b(1S) and eta_b(2S) states.
We search for CP violation in a sample of 20,000 Cabibbo-suppressed decays, $D^+\rightarrow K^+K^0_S\pi^+\pi^-$, and 30,000 Cabibbo-favored decays, $D_s^+\rightarrow K^+K^0_S\pi^+\pi^-$. We use 520 $fb^{-1}$ of data recorded by the BaBar detector at the PEP-II asymmetric-energy $e^+e^-$ collider operating at center of mass energies near 10.6 $GeV$. We search for CP violation in the difference between the $T$-odd asymmetries obtained using triple product correlations of the $D^+$ ($D_s^+$) and $D^-$ ($D_s^-$) decays, respectively. The $T$ violation parameter values obtained are $\mathcal{A}_T(D^+) = (-12.0 \pm 10.0_{stat} \pm 4.6_{syst})\times 10^{-3}$ and $\mathcal{A}_T(D_s^+) = (-13.6 \pm 7.7_{stat} \pm 3.4_{syst}) \times10^{-3}$, which are consistent with the Standard Model expectations.
We present a study of the decays B^{+-} --> D K^{+-} with D mesons reconstructed in the K+pi-pi0 or K-pi+pi0 final states, where D indicates a D0 or a anti-D0 meson. Using a sample of 474 million BBbar pairs collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC we obtain R^{+} = (5^{+12}_{-10}(stat) ^{+2}_{-4}(syst))\times10^{-3} and R^{-} = (12^{+12}_{-10}(stat) ^{+3}_{-5}(syst))\times10^{-3}, from which we extract the upper limits at 90% probability: R^+<23\times10^{-3} and R^-<29\times10^{-3}. Using these measurements, we obtain an upper limit for the ratio rB of the magnitudes of the b --> u and b --> c amplitudes r_B<0.13 at 90% probability.
We analyze the decay B0-->K+ pi- pi0 with a sample of 454 million B Bbar events collected by the BaBar detector at the PEP-II asymmetric-energy B factory at SLAC, and extract the complex amplitudes of seven interfering resonances over the Dalitz plot. These results are combined with amplitudes measured in B0-->K_S pi+ pi- decays to construct isospin amplitudes from B0-->K* pi and B0-->rho K decays. We measure the phase of the isospin amplitude Phi_3/2, useful in constraining the CKM unitarity triangle angle gamma and evaluate a CP rate asymmetry sum rule sensitive to the presence of new physics operators. We measure direct CP violation in B0-->K*+ pi- decays at the level of 3 sigma when measurements from both B0-->K+ pi- pi0 and B0-->K_S pi+ pi- decays are combined.
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