Limits on τ lepton-flavor violating decays into three charged leptons

A search for the neutrinoless, lepton-flavor violating decay of the τ lepton into three charged leptons has been performed using an integrated luminosity of 468  fb^(-1) collected with the BABAR detector at the PEP-II collider. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (1.8–3.3)×10^(-8) at 90% confidence level

Measurement of the γγ^*→η_c transition form factor

We study the reaction e^+e^-→e^+e^-η_c, η_c→K_SK^±π^∓ and obtain η_c mass and width values 2982.2±0.4±1.6  MeV/c^2 and 31.7±1.2±0.8  MeV, respectively. We find Γ(η_c→γγ)B(ηc→KK π)=0.374±0.009±0.031  keV, and measure the γγ^*→η_c transition form factor in the momentum transfer range from 2 to 50  GeV^2. The analysis is based on 469  fb^(-1) of integrated luminosity collected at PEP-II with the BABAR detector at e^+e^- center-of-mass energies near 10.6 GeV

Temperature dependence of the spin and orbital magnetization density in Sm1−xGdxAl2Sm_{1-x}Gd_{x} Al_{2} around the spin-orbital compensation point

Non-resonant ferromagnetic x-ray diffraction has been used to separate the spin and orbital contribution to the magnetization density of the proposed zero-moment ferromagnet $Sm_{0.982}Gd_{0.018} Al_{2}$. The alignment of the spin and orbital moments relative to the net magnetization shows a sign reversal at 84K, the compensation temperature. Below this temperature the orbital moment is larger than the spin moment, and vice versa above it. This result implies that the compensation mechanism is driven by the different temperature dependencies of the $4f$ spin and orbital moments. Specific heat data indicate that the system remains ferromagnetically ordered throughout

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 energy region above the Υ(4S) resonance. We use the inclusive yield of ϕ mesons and the ϕ 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 center-of-mass energy. The inclusive semileptonic branching fraction of the B_s meson is determined to be B(B_s→ℓνX)=9.5_(-2.0)^(+2.5)(stat)_(-1.9)^(+1.1)(syst)%, where ℓ indicates the average of e and μ

B^0 meson decays to ρ^0K^(*0), f_0K^(*0), and ρ^-K^(*+), including higher K^* resonances

We present branching fraction measurements for the decays B^0→ρ^0K^(*0), B^0→f_0K^(*0), and B^0→ρ^-K^(*+), where K^* is an S-wave (Kπ)_0^* or a K^*(892) meson; we also measure B^0→f_0K_2^*(1430)^0. For the K^*(892) channels, we report measurements of longitudinal polarization fractions (for ρ final states) and direct CP violation asymmetries. These results are obtained from a sample of (471.0±2.8)×10^6 BB̅ pairs collected with the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider at the SLAC National Accelerator Laboratory. We observe ρ^0K^*(892)^0, ρ^0(Kπ)_0^(*0), f_0K^*(892)^0, and ρ^-K^*(892)^+ with greater than 5σ significance, including systematics. We report first evidence for f_0(Kπ)_0^(*0) and f_0K_2^*(1430)^0, and place an upper limit on ρ^-(Kπ)_0^(*+). Our results in the K^*(892) channels are consistent with no direct CP violation

Search for the decay D^0 → γγ and measurement of the branching fraction for D^0 → π^0π^0

We search for the rare decay of the D^0 meson to two photons, D^0→γγ, and present a measurement of the branching fraction for a D^0 meson decaying to two neutral pions, B(D^0→π^0π^0). The data sample analyzed corresponds to an integrated luminosity of 470.5  fb^(-1) collected by the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider at SLAC. We place an upper limit on the branching fraction, B(D^0→γγ)<2.2×10^(-6), at 90% confidence level. This limit improves on the existing limit by an order of magnitude. We also find B(D^0→π^0π^0)=(8.4±0.1±0.4±0.3)×10^(-4)

Study of Y(3S,2S) → ηY(1S) and Y(3S,2S) → π^+π^-Y(1S) hadronic transitions

We study the Υ(3S,2S)→ηΥ(1S) and Υ(3S,2S)→π^+π^-Υ(1S) transitions with 122×10^6Υ(3S) and 100×10^6Υ(2S) mesons collected by the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider. We measure B[Υ(2S)→ηΥ(1S)]=(2.39±0.31(stat.)±0.14(syst.))×10^(-4) and Γ[Υ(2S)→ηΥ(1S)]/Γ[Υ(2S)→π^+π^-Υ(1S)]=(1.35±0.17(stat.)±0.08(syst.))×10^(-3). We find no evidence for Υ(3S)→ηΥ(1S) and obtain B[Υ(3S)→ηΥ(1S)]<1.0×10^(-4) and Γ[Υ(3S)→ηΥ(1S)]/ Γ[Υ(3S)→π^+π^-Υ(1S)]<2.3×10^(-3) as upper limits at the 90% confidence level. We also provide improved measurements of the Υ(2S)-Υ(1S) and Υ(3S)-Υ(1S) mass differences, 562.170±0.007(stat.)±0.088(syst.)  MeV/c^2 and 893.813±0.015(stat.)±0.107(syst.)  MeV/c^2, respectively

Search for CP violation in the decay τ-→π-K_S^0(≥0π^0)ν_τ

We report a search for CP violation in the decay τ-→π-KS^0(≥0π^0)ντ using a data set of 437×10^6 τ-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 (-0.36±0.23±0.11)% approximately 2.8 standard deviations from the standard model prediction of (0.36±0.01)%