Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-

We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi --> D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7 J/Psi events collected with the BESII detector at the BEPC. No excess of signal above background is observed, and 90% confidence level upper limits on the branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi --> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure

Study of J/psi decays to Lambda Lambdabar and Sigma0 Sigma0bar

The branching ratios and Angular distributions for J/psi decays to Lambda Lambdabar and Sigma0 Sigma0bar are measured using BESII 58 million J/psi.Comment: 11 pages, 5 figure

Measurement of \chi_cJ--> K+K-K+K-

Using 14M psi(2S) events taken with the BES-II detector, chi_cJ-->K+K-K+K- decays are studied. For the four-kaon final state, the branching fractions are B(chi_c0,1,2 -->K+K-K+K-)=(3.48\pm 0.23\pm 0.47)\times 10^{-3}, (0.70\pm 0.13\pm 0.10)\times 10^{-3}, and (2.17\pm 0.20\pm 0.31)\times 10^{-3}. For the \phi K+K- final state, the branching fractions, which are measured for the first time, are B(chi_c0,1,2-->\phi K+K-)=(1.03\pm 0.22\pm 0.15)\times 10^{-3}, (0.46\pm 0.16\pm 0.06)\times 10^{-3}, and (1.67\pm 0.26\pm 0.24)\times 10^{-4}. For the \phi\phi final state, B(chi_{c0,2}-->\phi\phi)=(0.94\pm 0.21\pm 0.13)\times 10^{-3} and (1.70\pm 0.30\pm 0.25)\times 10^{-3}.Comment: 7 pages, 7 figure

Partial wave analyses of J/psi to gamma pi^+ pi^- and gamma pi^0 pi^0

Results are presented on J/psi radiative decays to pi^+pi^- and pi^0pi^0 based on a sample of 58M J/psi events taken with the BESII detector. Partial wave analyses are carried out using the relativistic covariant tensor amplitude method in the 1.0 to 2.3 GeV/c^2 pipi mass range. There are conspicuous peaks due to the f_2(1270) and two 0^++ states in the 1.45 and 1.75 GeV/c^2 mass regions. The first 0^++ state has a mass of 1466\pm 6\pm 20 MeV/c^2, a width of 108^{+14}_{-11}\pm 25 MeV/c^2, and a branching fraction B(J/psi \to \gamma f_0(1500) \to\gamma \pi^+\pi^-) = (0.67\pm0.02\pm0.30) \times 10^{-4}. Spin 0 is strongly preferred over spin 2. The second 0^++ state peaks at 1765^{+4}_{-3}\pm 13 MeV/c^2 with a width of 145\pm8\pm69 MeV/c^2. If this 0^++ is interpreted as coming from f_0(1710), the ratio of its branching fractions to pipi and K\bar K is 0.41^{+0.11}_{-0.17}.Comment: 9 pages, 6 figure

Evidence for kappa Meson Production in J/psi -> bar{K}^*(892)^0K^+pi^- Process

Based on 58 million BESII J/psi events, the bar{K}^*(892)^0K^+pi^- channel in K^+K^-pi^+pi^- is studied. A clear low mass enhancement in the invariant mass spectrum of K^+pi^- is observed. The low mass enhancement does not come from background of other J/psi decay channels, nor from phase space. Two independent partial wave analyses have been performed. Both analyses favor that the low mass enhancement is the kappa, an isospinor scalar resonant state. The average mass and width of the kappa in the two analyses are 878 +- 23^{+64}_{-55} MeV/c^2 and 499 +- 52^{+55}_{-87} MeV/c^2, respectively, corresponding to a pole at (841 +- 30^{+81}_{-73}) - i(309 +- 45^{+48}_{-72}) MeV/c^2.Comment: 17 pages, 5 figure

Precison Measurements of the Mass, the Widths of ψ(3770)\psi(3770) Resonance and the Cross Section σ[e+e−→ψ(3770)]\sigma[e^+e^-\to \psi(3770)] at Ecm=3.7724E_{\rm cm}=3.7724 GeV

By analyzing the $R$ values measured at 68 energy points in the energy region between 3.650 and 3.872 GeV reported in our previous paper, we have precisely measured the mass, the total width, the leptonic width and the leptonic decay branching fraction of the $\psi(3770)$ to be ${M}_{\psi(3770)}=3772.4 \pm 0.4 \pm 0.3$ MeV, $\Gamma_{\psi(3770)}^{\rm tot} = 28.6 \pm 1.2 \pm 0.2$ MeV, $\Gamma_{\psi(3770)}^{ee} = 279 \pm 11 \pm 13$ eV and $B[\psi(3770)\to e^+e^-]=(0.98\pm 0.04\pm 0.04)\times 10^{-5}$, respectively, which result in the observed cross section $\sigma^{\rm obs}[e^+e^-\to \psi(3770)]=7.25\pm 0.27 \pm 0.34$ nb at $\sqrt{s}=3772.4$ MeV. We have also measured $R_{\rm uds}=2.121\pm 0.023 \pm 0.084$ for the continuum light hadron production in the region from 3.650 to 3.872 GeV.Comment: 5 pages, 2 figure

Measurements of the cross sections for e+e−→hadronse^+e^- \to {\rm hadrons} at 3.650, 3.6648, 3.773 GeV and the branching fraction for ψ(3770)→non−DDˉ\psi(3770)\to {\rm non-}D\bar D

Using the BES-II detector at the BEPC Collider, we measured the lowest order cross sections and the $R$ values ($R=\sigma^0_{e^+e^- \to {\rm hadrons}}/\sigma^0_{e^+e^- \to \mu^+\mu^-}$) for inclusive hadronic event production at the center-of-mass energies of 3.650 GeV, 3.6648 GeV and 3.773 GeV. The results lead to $\bar R_{uds}=2.224\pm 0.019\pm 0.089$ which is the average of these measured at 3.650 GeV and 3.6648 GeV, and $R=3.793\pm 0.037 \pm 0.190$ at $\sqrt{s}=3.773$ GeV. We determined the lowest order cross section for $\psi(3770)$ production to be $\sigma^{\rm B}_{\psi(3770)} = (9.575\pm 0.256 \pm 0.813)~{\rm nb}$ at 3.773 GeV, the branching fractions for $\psi(3770)$ decays to be $BF(\psi(3770) \to D^0\bar D^0)=(48.9 \pm 1.2 \pm 3.8)$, $BF(\psi(3770) \to D^+ D^-)=(35.0 \pm 1.1 \pm 3.3)$ and $BF(\psi(3770) \to D\bar{D})=(83.9 \pm 1.6 \pm 5.7)$, which result in the total non-$D\bar D$ branching fraction of $\psi(3770)$ decay to be $BF(\psi(3770) \to {\rm non}-D\bar D)=(16.1 \pm 1.6 \pm 5.7)$.Comment: 11 pages, 5 figure

Track A Basic Science

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138319/1/jia218438.pd

Gamma Prime Precipitate Evolution During Aging of a Model Nickel-Based Superalloy

The microstructural stability of nickel-based superalloys is critical for maintaining alloy performance during service in gas turbine engines. In this study, the precipitate evolution in a model polycrystalline Ni-based superalloy during aging to 1000 hours has been studied via transmission electron microscopy, atom probe tomography and neutron diffraction. Variations in phase composition and precipitate morphology, size and volume fraction were observed during aging, whilst the constrained lattice misfit remained constant at approximately zero. The experimental composition of the γ matrix phase was consistent with thermodynamic equilibrium predictions, whilst significant differences were identified between the experimental and predicted results from the γʹ phase. These results have implications for the evolution of mechanical properties in service and their prediction using modeling methods.The authors wish to acknowledge Mrs. S. Rhodes, Dr. H.T. Pang, Dr. D.M. Collins, and Dr. O.M.D.M. Messé for their assistance with the experiments performed. Funding was provided by the EPSRC/Rolls-Royce Strategic Partnership under EP/M005607/1 and EP/H022309/1. The Oxford Atom Probe facility was funded by the EPSRC under EP/M022803/1. Neutron diffraction beam time was supported through the Canadian Neutron Beam Centre under Experiment number 1258