Cross sections for the reactions $e^+ e^-to K_S^0 K_L^0$, $K_S^0 K_L^0 pi^+pi^-$, $K_S^0 K_S^0 pi^+pi^-$, and $K_S^0 K_S^0 K^+K^-$ from events with initial-state radiation

We study the processes $e^+ e^-to K_S^0 K_L^0 gamma$, $K_S^0 K_L^0 pi^+pi^-gamma$, $K_S^0 K_S^0 pi^+pi^-gamma$, and $K_S^0 K_S^0 K^+K^-gamma$, where the photon is radiated from the initial state, providing cross section measurements for the hadronic states over a continuum of center-of-mass energies. The results are based on 469 fb$^{-1}$ of data collected with the BaBar detector at SLAC. We observe the $phi(1020)$ resonance in the $K_S^0 K_L^0$ final state and measure the product of its electronic width and branching fraction with about 3% uncertainty. We present a measurement of the $e^+ e^-to K_S^0 K_L^0 $ cross section in the energy range from 1.06 to 2.2 GeV and observe the production of a resonance at 1.67 GeV. We present the first measurements of the $e^+ e^-to K_S^0 K_L^0 pi^+pi^-$, $K_S^0 K_S^0 pi^+pi^-$, and $K_S^0 K_S^0 K^+K^-$ cross sections, and study the intermediate resonance structures. We obtain the first observations of jpsi decay to the $K_S^0 K_L^0 pi^+pi^-$, $K_S^0 K_S^0 pi^+pi^-$, and $K_S^0 K_S^0 K^+K^-$ final states.

Evidence for the decay B0 --> omega omega and search for B0 --> omega phi

We describe searches for B meson decays to the charmless vector-vector final states omega omega and omega phi with 471 x 10^6 B Bbar pairs produced in e+ e- annihilation at sqrt(s) = 10.58 GeV using the BABAR detector at the PEP-II collider at the SLAC National Accelerator Laboratory. We measure the branching fraction B(B0 --> omega omega) = (1.2 +- 0.3 +0.3-0.2) x 10^-6, where the first uncertainty is statistical and the second is systematic, corresponding to a significance of 4.4 standard deviations. We also determine the upper limit B(B0 --> omega phi) < 0.7 x 10^-6 at 90% confidence level. These measurements provide the first evidence for the decay B0 --> omega omega, and an improvement of the upper limit for the decay B0 --> omega phi.

Study of the decay $bar{B}^{0}rightarrowLambda_{c}^{+}bar{p}pi^{+}pi^{-}$ and its intermediate states

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 storage 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.

Observation of Time Reversal Violation in the B0 Meson System

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.

A Measurement of the Semileptonic Branching Fraction of the B_s Meson

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.

Observation of the rare decay B+->K+pi0pi0 and measurement of the quasi-two body contributions B+->K*(892)+pi0, B+->f0(980)K+ and B+->chic0K+

We report an analysis of the charmless hadronic decays of charged B meson to the final state K+pi0pi0, using a data sample of 470+/-2.8 million BBbar events collected at the Y(4S) resonance. We observe an excess of signal events, with a significance above 10 standard deviations including systematic uncertainties, and measure the branching fraction and CP asymmetry to be B(B+->K+pi0pi0)=(16.2+/-1.2+/-1.5)x10^-6 and A_CP(B+->K+pi0pi0)=-0.06+/-0.06+/-0.04, where the uncertainties are statistical and systematic respectively. Additionally we study the contributions of the B+->K*(892)+pi0, B+->f0(980)K+ and B+->chic0K+ quasi-two body decays. We report the worlds best measurements of the branching fractions and CP asymmetry of the B+->K+pi0pi0 and B+->K*(892)+pi0 channels.

Search for hadronic decays of a light Higgs boson in the radiative decay Upsilon --> gamma A0

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.

Observation of the baryonic B decay B0bar --> Lambda_c^+ anti-Lambda K-

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.

Study of radiative bottomonium transitions using converted photons

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.

Evidence for the h_b(1P) meson in the decay Upsilon(3S) --> pi0 h_b(1P)

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_{bJ}(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.) +/- 2(syst.) MeV/c^2. The width of the observed signal is consistent with experimental resolution, and its significance is 3.1sigma, including systematic uncertainties. We obtain the value (4.3 +/- 1.1(stat.) +/- 0.9(syst.)) x 10^{-4} for the product branching fraction BF(Upsilon(3S)-->pi0 h_b) x BF(h_b-->gamma eta_b).