983 research outputs found

    Modification of the alpha-Ti laths to near equiaxed alpha-Ti grains in as-sintered titanium and titanium alloys by a small addition of boron

    Get PDF
    A small addition of boron (B) changes the morphology of the α-Ti laths in as-sintered Ti-6Al-4V and Ti- 10 V-2Fe-3Al to near equiaxed α-Ti grains and increases the number density of the resulting α-Ti grains by up to six folds. TiB forms at about 700 °C during heating to the isothermal sintering temperature and more than 90% of the TiB particles were found inside the α-Ti grains. Transmission electron microscopy (TEM) was used to identify the orientation relationships (ORs) between the TiB and α-Ti phases. Their exact ORs are affected by both the chemistry of the alloy and the processing conditions. The modification of the α-Ti laths and the substantial increase in the number density of the α-Ti grains are attributed to the enhanced heterogeneous nucleation of α-Ti on TiB due to the identified specific ORs and excellent lattice matches between these two phases. In addition, there exists a unique peritectoid reaction between b-Ti and TiB during the subsequent cooling after isothermal sintering by which-Ti + TiB → α-Ti, which may have contributed to the enhanced heterogeneous nucleation of α-Ti on TiB

    Direct Measurements of the Branching Fractions for D0→K−e+νeD^0 \to K^-e^+\nu_e and D0→π−e+νeD^0 \to \pi^-e^+\nu_e and Determinations of the Form Factors f+K(0)f_{+}^{K}(0) and f+π(0)f^{\pi}_{+}(0)

    Get PDF
    The absolute branching fractions for the decays D0→K−e+νeD^0 \to K^-e ^+\nu_e and D0→π−e+νeD^0 \to \pi^-e^+\nu_e are determined using 7584±198±3417584\pm 198 \pm 341 singly tagged Dˉ0\bar D^0 sample from the data collected around 3.773 GeV with the BES-II detector at the BEPC. In the system recoiling against the singly tagged Dˉ0\bar D^0 meson, 104.0±10.9104.0\pm 10.9 events for D0→K−e+νeD^0 \to K^-e ^+\nu_e and 9.0±3.69.0 \pm 3.6 events for D0→π−e+νeD^0 \to \pi^-e^+\nu_e decays are observed. Those yield the absolute branching fractions to be BF(D0→K−e+νe)=(3.82±0.40±0.27)BF(D^0 \to K^-e^+\nu_e)=(3.82 \pm 0.40\pm 0.27)% and BF(D0→π−e+νe)=(0.33±0.13±0.03)BF(D^0 \to \pi^-e^+\nu_e)=(0.33 \pm 0.13\pm 0.03)%. The vector form factors are determined to be ∣f+K(0)∣=0.78±0.04±0.03|f^K_+(0)| = 0.78 \pm 0.04 \pm 0.03 and ∣f+π(0)∣=0.73±0.14±0.06|f^{\pi}_+(0)| = 0.73 \pm 0.14 \pm 0.06. The ratio of the two form factors is measured to be ∣f+π(0)/f+K(0)∣=0.93±0.19±0.07|f^{\pi}_+(0)/f^K_+(0)|= 0.93 \pm 0.19 \pm 0.07.Comment: 6 pages, 5 figure

    Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta

    Full text link
    Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector, the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and (7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure

    BESII Detector Simulation

    Full text link
    A Monte Carlo program based on Geant3 has been developed for BESII detector simulation. The organization of the program is outlined, and the digitization procedure for simulating the response of various sub-detectors is described. Comparisons with data show that the performance of the program is generally satisfactory.Comment: 17 pages, 14 figures, uses elsart.cls, to be submitted to NIM

    Measurement of branching fractions for the inclusive Cabibbo-favored ~K*0(892) and Cabibbo-suppressed K*0(892) decays of neutral and charged D mesons

    Full text link
    The branching fractions for the inclusive Cabibbo-favored ~K*0 and Cabibbo-suppressed K*0 decays of D mesons are measured based on a data sample of 33 pb-1 collected at and around the center-of-mass energy of 3.773 GeV with the BES-II detector at the BEPC collider. The branching fractions for the decays D+(0) -> ~K*0(892)X and D0 -> K*0(892)X are determined to be BF(D0 -> \~K*0X) = (8.7 +/- 4.0 +/- 1.2)%, BF(D+ -> ~K*0X) = (23.2 +/- 4.5 +/- 3.0)% and BF(D0 -> K*0X) = (2.8 +/- 1.2 +/- 0.4)%. An upper limit on the branching fraction at 90% C.L. for the decay D+ -> K*0(892)X is set to be BF(D+ -> K*0X) < 6.6%

    Study of J/ψ→ωK+K−J/\psi \to \omega K^+K^-

    Get PDF
    New data are presented on J/ψ→ωK+K−J/\psi \to \omega K^+K^- from a sample of 58M J/ψJ/\psi events in the upgraded BES II detector at the BEPC. There is a conspicuous signal for f0(1710)→K+K−f_0(1710) \to K^+K^- and a peak at higher mass which may be fitted with f2(2150)→KKˉf_2(2150) \to K\bar K. From a combined analysis with ωπ+π−\omega \pi ^+ \pi ^- data, the branching ratio BR(f0(1710)→ππ)/BR(f0(1710)→KKˉ)BR(f_0(1710)\to\pi\pi)/BR(f_0(1710) \to K\bar K) is <0.11< 0.11 at the 95% confidence level.Comment: 11 pages, 5 figures. Submitted to Phys. Lett.

    The σ\sigma pole in J/ψ→ωπ+π−J/\psi \to \omega \pi^+ \pi^-

    Full text link
    Using a sample of 58 million J/ψJ/\psi events recorded in the BESII detector, the decay J/ψ→ωπ+π−J/\psi \to \omega \pi^+ \pi^- is studied. There are conspicuous ωf2(1270)\omega f_2(1270) and b1(1235)πb_1(1235)\pi signals. At low ππ\pi \pi mass, a large broad peak due to the σ\sigma is observed, and its pole position is determined to be (541±39)(541 \pm 39) - ii (252±42)(252 \pm 42) MeV from the mean of six analyses. The errors are dominated by the systematic errors.Comment: 15 pages, 6 figures, submitted to PL

    Search for the Lepton Flavor Violation Processes J/ψ→J/\psi \to μτ\mu\tau and eτe\tau

    Full text link
    The lepton flavor violation processes J/ψ→μτJ/\psi \to \mu\tau and eτe\tau are searched for using a sample of 5.8×107\times 10^7 J/ψJ/\psi events collected with the BESII detector. Zero and one candidate events, consistent with the estimated background, are observed in J/ψ→μτ,τ→eνˉeντJ/\psi \to \mu\tau, \tau\to e\bar\nu_e\nu_{\tau} and J/ψ→eτ,τ→μνˉμντJ/\psi\to e\tau, \tau\to\mu\bar\nu_{\mu}\nu_{\tau} decays, respectively. Upper limits on the branching ratios are determined to be Br(J/ψ→μτ)<2.0×10−6Br(J/\psi\to\mu\tau)<2.0 \times 10^{-6} and Br(J/ψ→eτ)<8.3×10−6Br(J/\psi \to e\tau) < 8.3 \times10^{-6} at the 90% confidence level (C.L.).Comment: 9 pages, 2 figure

    Microwave heating, isothermal sintering, and mechanical properties of powder metallurgy titanium and titanium alloys

    Get PDF
    This article presents a detailed assessment of microwave (MW) heating, isothermal sintering, and the resulting tensile properties of commercially pure Ti (CP-Ti), Ti-6Al-4V, and Ti-10V-2Fe-3Al (wt pct), by comparison with those fabricated by conventional vacuum sintering. The potential of MW sintering for titanium fabrication is evaluated accordingly. Pure MW radiation is capable of heating titanium powder to ≥1573 K (1300 C), but the heating response is erratic and difficult to reproduce. In contrast, the use of SiC MW susceptors ensures rapid, consistent, and controllable MW heating of titanium powder. MW sintering can consolidate CP-Ti and Ti alloys compacted from -100 mesh hydride-dehydride (HDH) Ti powder to ~95.0 pct theoretical density (TD) at 1573 K (1300 C), but no accelerated isothermal sintering has been observed over conventional practice. Significant interstitial contamination occurred from the Al2O3-SiC insulation-susceptor package, despite the high vacuum used (≤4.0 × 10-3 Pa). This leads to erratic mechanical properties including poor tensile ductility. The use of Ti sponge as impurity (O, N, C, and Si) absorbers can effectively eliminate this problem and ensure good-to-excellent tensile properties for MW-sintered CP-Ti, Ti-10V-2Fe-3Al, and Ti-6Al-4V. The mechanisms behind various observations are discussed. The prime benefit of MW sintering of Ti powder is rapid heating. MW sintering of Ti powder is suitable for the fabrication of small titanium parts or titanium preforms for subsequent thermomechanical processing

    Measurements of Cabibbo Suppressed Hadronic Decay Fractions of Charmed D0 and D+ Mesons

    Full text link
    Using data collected with the BESII detector at e+e−e^{+}e^{-} storage ring Beijing Electron Positron Collider, the measurements of relative branching fractions for seven Cabibbo suppressed hadronic weak decays D0→K−K+D^0 \to K^- K^+, π+π−\pi^+ \pi^-, K−K+π+π−K^- K^+ \pi^+ \pi^- and π+π+π−π−\pi^+ \pi^+ \pi^- \pi^-, D+→K0ˉK+D^+ \to \bar{K^0} K^+, K−K+π+K^- K^+ \pi^+ and π−π+π+\pi^- \pi^+ \pi^+ are presented.Comment: 11 pages, 5 figure
    • …
    corecore