We present a search for nine lepton-number-violating and three lepton-flavor-violating neutral charm decays of the type D^{0}→h^{'-}h^{-}ℓ^{'+}ℓ^{+} and D^{0}→h^{'-}h^{+}ℓ^{'±}ℓ^{∓}, where h and h^{'} represent a K or π meson and ℓ and ℓ^{'} an electron or muon. The analysis is based on 468  fb^{-1} of e^{+}e^{-} annihilation data collected at or close to the ϒ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory. No significant signal is observed for any of the twelve modes, and we establish 90% confidence level upper limits on the branching fractions in the range (1.0-30.6)×10^{-7}. The limits are between 1 and 3 orders of magnitude more stringent than previous measurements.

We study the processes e+e-→KS0KL0π0γ, KS0KL0ηγ, and KS0KL0π0π0γ, where the photon is radiated from the initial state, providing cross section measurements for the hadronic final states over a continuum of center-of-mass energies. The results are based on 469 fb-1 of data collected at or near the ϒ(4S) resonance with the BABAR detector at SLAC. We present the first measurements of the e+e-→KS0KL0π0, KS0KL0η, and KS0KL0π0π0 cross sections up to a center-of-mass energy of 4 GeV and study their intermediate resonance structures. We observe J/ψ decays to all of these final states for the first time, present measurements of their J/ψ branching fractions, and search for ψ(2S) decays.

Using the eight time dependences e-Γt(1+CicosΔmt+SisinΔmt) for the decays ϒ(4S)→B0B 0→fjfk, with the decay into a flavor-specific state fj=±X before or after the decay into a CP eigenstate fk=cc KS,L, as measured by the BABAR experiment, we determine the three CPT-sensitive parameters Re(z) and Im(z) in B0-B 0 mixing and |Ā/A| in B0→cc K0 decays. We find Im(z)=0.010±0.030±0.013, Re(z)=-0.065±0.028±0.014, and |Ā/A|=0.999±0.023±0.017, in agreement with CPT symmetry.

We study the processes e+e-→γISRJ/ψ, where J/ψ→π+π-π0, J/ψ→K+K-π0, and J/ψ→KS0K±π∓ using a data sample of 519 fb-1 recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e+e- collider at center-of-mass energies at and near the ϒ(nS) (n=2,3,4) resonances. We measure the ratio of branching fractions R1=B(J/ψ→K+K-π0)B(J/ψ→π+π-π0) and R2=B(J/ψ→KS0K±π∓)B(J/ψ→π+π-π0). We perform Dalitz plot analyses of the three J/ψ decay modes and measure fractions for resonances contributing to the decays. We also analyze the J/ψ→π+π-π0 decay using the Veneziano model. We observe structures compatible with the presence of ρ(1450) in all three J/ψ decay modes and measure the relative branching fraction: R(ρ(1450))=B(ρ(1450)→K+K-)B(ρ(1450)→π+π-)=0.307±0.084(stat)±0.082(sys).

We study the processes e+e-→π+π-π0π0π0π0γ and π+π-π0π0π0ηγ in which an energetic photon is radiated from the initial state. The data were collected with the BABAR detector at the SLAC National Accelerator Laboratory. About 7300 and 870 events, respectively, are selected from a data sample corresponding to an integrated luminosity of 469 fb-1. The invariant mass of the hadronic final state defines the effective e+e- center-of-mass energy. The center-of-mass energies range from threshold to 4.5 GeV. From the mass spectra, the first ever measurements of the e+e-→π+π-π0π0π0π0 and the e+e-→π+π-π0π0π0η cross sections are performed. The contributions from ωπ0π0π0, ηπ+π-π0, ωη, and other intermediate states are presented. We observe the J/ψ and ψ(2S) in most of these final states and measure the corresponding branching fractions, many of them for the first time.

Based on a sample of 500 million e+e-→cc¯ events recorded by the BABAR detector at c.m. energies of close to 10.6 GeV, we report on a study of the decay D0→π-e+νe. We measure the ratio of branching fractions, RD=B(D0→π-e+νe)/B(D0→K-π+)=0.0713±0.0017stat±0.0024syst, and use the present world average for B(D0→K-π+) to obtain B(D0→π-e+νe)=(2.770±0.068stat±0.092syst±0.037ext)×10-3 where the third error accounts for the uncertainty on the branching fraction for the reference channel. The measured dependence of the differential branching fraction on q2, the four-momentum transfer squared between the D and the π meson, is compared to various theoretical predictions for the hadronic form factor, f+,Dπ(q2), and the normalization |Vcd|×f+,Dπ(q2=0)=0.1374±0.0038stat±0.0022syst±0.0009ext. is extracted from a fit to data. Using the most recent LQCD prediction of f+,Dπ(q2=0)=0.666±0.029, we obtain |Vcd|=0.206±0.007exp±0.009LQCD. Assuming, instead, |Vcd|=|Vus|=0.2252±0.0009, we obtain f+,Dπ(q2=0)=0.610±0.020exp±0.005ext. The q2 dependence of f+,Dπ(q2) is compared to a variety of multipole parametrizations. This information is applied to B0→π-e+νe decays and, combined with an earlier B0→π-e+νe measurement by BABAR, is used to derive estimates of |Vub|.

We study the (1S) radiative decays to γπ+π- and γK+K- using data recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e+e- collider at center-of-mass energies at the (2S) and (3S) resonances. The (1S) resonance is reconstructed from the decay (nS)→π+π-(1S), n=2, 3. Branching fraction measurements and spin-parity analyses of (1S) radiative decays are reported for the I=0 S-wave and f2(1270) resonances in the π+π- mass spectrum, the f2′(1525) and f0(1500) in the K+K- mass spectrum, and the f0(1710) in both.

We use (121±1) million Υ(3S) and (98±1) million Υ(2S) mesons recorded by the BABAR detector at the PEP-II e+e- collider at SLAC to perform a study of radiative transitions involving the χbJ(1P,2P) states in exclusive decays with μ+μ-γγ final states. We reconstruct twelve channels in four cascades using two complementary methods. In the first we identify both signal photon candidates in the electromagnetic calorimeter (EMC), employ a calorimeter timing-based technique to reduce backgrounds, and determine branching-ratio products and fine mass splittings. These results include the best observational significance yet for the χb0(2P)→γΥ(2S) and χb0(1P)→γΥ(1S) transitions. In the second method, we identify one photon candidate in the EMC and one which has converted into an e+e- pair due to interaction with detector material, and we measure absolute product branching fractions. This method is particularly useful for measuring Υ(3S)→γχb1,2(1P) decays. Additionally, we provide the most up-to-date derived branching fractions, matrix elements and mass splittings for χb transitions in the bottomonium system. Using a new technique, we also measure the two lowest-order spin-dependent coefficients in the nonrelativistic QCD Hamiltonian.

A study of the two-body decays B^{±}→X_{cc[over ¯]}K^{±}, where X_{cc[over ¯]} refers to one charmonium state, is reported by the BABAR Collaboration using a data sample of 424  fb^{-1}. The absolute determination of branching fractions for these decays are significantly improved compared to previous BABAR measurements. Evidence is found for the decay B^{+}→X(3872)K^{+} at the 3σ level. The absolute branching fraction B[B^{+}→X(3872)K^{+}]=[2.1±0.6(stat)±0.3(syst)]×10^{-4} is measured for the first time. It follows that B[X(3872)→J/ψπ^{+}π^{-}]=(4.1±1.3)%, supporting the hypothesis of a molecular component for this resonance.