Spectral function of the electron in a superconducting RVB state

We present a model calculation of the spectral function of an electron in a superconducting resonating valence bond (RVB) state. The RVB state, described by the phase-string mean field theory is characterized by three important features: (i) spin-charge separation, (ii) short range antiferromagnetic correlations, and (iii) holon condensation. The results of our calculation are in good agreement with data obtained from Angle Resolved Photoemission Spectroscopy (ARPES) in superconducting Bi 2212 at optimal doping concentration.Comment: 4 pages, 3 figure

Measurements of the observed cross sections for exclusive light hadron production in e^+e^- annihilation at \sqrt{s}= 3.773 and 3.650 GeV

By analyzing the data sets of 17.3 pb$^{-1}$ taken at $\sqrt{s}=3.773$ GeV and 6.5 pb$^{-1}$ taken at $\sqrt{s}=3.650$ GeV with the BESII detector at the BEPC collider, we have measured the observed cross sections for 12 exclusive light hadron final states produced in $e^+e^-$ annihilation at the two energy points. We have also set the upper limits on the observed cross sections and the branching fractions for $\psi(3770)$ decay to these final states at 90% C.L.Comment: 8 pages, 5 figur

Measurements of psi(2S) decays to octet baryon-antibaryon pairs

With a sample of 14 million psi(2S) events collected by the BESII detector at the Beijing Electron Positron Collider (BEPC), the decay channels psi(2S)->p p-bar, Lambda Lambda-bar, Sigma0 Sigma0-bar, Xi Xi-bar are measured, and their branching ratios are determined to be (3.36+-0.09+-0.24)*10E-4, (3.39+-0.20+-0.32)*10E-4, (2.35+-0.36+-0.32)*10E-4, (3.03+-0.40+-0.32)*10E-4, respectively. In the decay psi(2S)->p p-bar, the angular distribution parameter alpha is determined to be 0.82+-0.17+-0.04.Comment: 8 pages, 8 figure

Direct measurement of the absolute branching fraction for D+→Kˉ0μ+νμD^+ \to {\bar K}^0\mu^+\nu_\mu and determination of Γ(D0→K−μ+νμ)/Γ(D+→Kˉ0μ+νμ) \Gamma (D^0 \to K^-\mu^+\nu_\mu)/\Gamma (D^+ \to {\bar K}^0\mu^+\nu_\mu)

The absolute branching fraction for the decay $D^+ \to {\bar K}^0\mu^+\nu_\mu$ is determined using $5321 \pm 149 \pm160$ singly tagged $D^-$ sample from the data collected around 3.773 GeV with the BESII detector at the BEPC collider. In the system recoiling against the singly tagged $D^-$ mesons, $28.7 \pm 6.4$ events for $D^+ \to {\bar K}^0\mu^+\nu_\mu$ are observed. These yield the absolute branching fraction to be $BF(D^+ \to {\bar K}^0\mu^+\nu_\mu) = (10.3\pm2.3\pm0.8)$. The ratio of the two partial widths for the decays $D^0 \to K^-\mu^+\nu_\mu$ and $D^+ \to {\bar K}^0\mu^+\nu_\mu$ is determined to be $\Gamma (D^0 \to K^-\mu^+\nu_\mu)/\Gamma (D^+ \to {\bar K}^0\mu^+\nu_\mu) = 0.87 \pm 0.24 \pm 0.15$.Comment: 6 pages, 5 figure

Anomalous Line-Shape of Cross Sections for e+e−→Hadronse^+e^- \to {\rm Hadrons} in the Center-of-Mass Energy Region between 3.650 and 3.872 GeV

We observe an obvious anomalous line-shape of the $e^+e^- \to {\rm hadrons}$ total cross sections in the energy region between 3.700 and 3.872 GeV from the data samples taken with the BES-II detector at the BEPC Collider. Re-analysis of the data shows that it is inconsistent with the explanation for only one simple $\psi(3770)$ resonance with a statistical significance of $7\sigma$. The anomalous line-shape may be explained by two possible enhancements of the inclusive hadron production near the center-of-mass energies of 3.764 GeV and 3.779 GeV, indicating that either there is likely a new structure in addition to the $\psi(3770)$ resonance around 3.773 GeV, or there are some physics effects reflecting the $D\bar D$ production dynamics

First observation of J/\psi and \psi(2S) decaying to n K^0_S\bar\Lambda +c.c

The decays of \jpsi and \psip to ${n}{K^0_S}\bar{\Lambda}+c.c.$ are observed and measured for the first time, and the perturbative QCD ``12%'' rule is tested, based on $5.8 \times 10^7$ \jpsi and $1.4 \times 10^7$ \psip events collected with BESII detector at the Beijing Electron-Positron Collider. No obvious enhancement near $n\bar{\Lambda}$ threshold in \jpsi \to {n}{K^0_S}\bar{\Lambda}+c.c. is observed, and the upper limit on the branching ratio of \jpsi \to {K^0_S} X, X \to n \bar \Lambda is determined.Comment: 10 pages, 10 figure

Study of J\psi decaying into \omega p \bar p

The decay $J/\psi \to \omega p \bar p$ is studied using a $5.8 \times 10^7$ $J/\psi$ event sample accumulated with the BES II detector at the Beijing electron-positron collider. The decay branching fraction is measured to be $B(J/\psi \to \omega p \bar p)=(9.8\pm 0.3\pm 1.4)\times 10^{-4}$. No significant enhancement near the $p\bar p$ mass threshold is observed, and an upper limit of $B(J/\psi \to \omega X(1860))B(X(1860)\to p\bar p)$$$$< 1.5 \times 10^{-5}$ is determined at the 95% confidence level, where X(1860) designates the near-threshold enhancement seen in the $p\bar p$ mass spectrum in $J/\psi \to \gamma p \bar p$ decays.Comment: 5 pages, 4 figure

Comparing proton momentum distributions in A=2A=2 and 3 nuclei via 2^2H 3^3H and 3^3He (e,e′p)(e, e'p) measurements

We report the first measurement of the $(e,e'p)$ reaction cross-section ratios for Helium-3 ($^3$He), Tritium ($^3$H), and Deuterium ($d$). The measurement covered a missing momentum range of $40 \le p_{miss} \le 550$ MeV$/c$, at large momentum transfer ($\langle Q^2 \rangle \approx 1.9$ (GeV$/c$)$^2$) and $x_B>1$, which minimized contributions from non quasi-elastic (QE) reaction mechanisms. The data is compared with plane-wave impulse approximation (PWIA) calculations using realistic spectral functions and momentum distributions. The measured and PWIA-calculated cross-section ratios for $^3$He$/d$ and $^3$H$/d$ extend to just above the typical nucleon Fermi-momentum ($k_F \approx 250$ MeV$/c$) and differ from each other by $\sim 20\%$, while for $^3$He/$^3$H they agree within the measurement accuracy of about 3\%. At momenta above $k_F$, the measured $^3$He/$^3$H ratios differ from the calculation by $20\% - 50\%$. Final state interaction (FSI) calculations using the generalized Eikonal Approximation indicate that FSI should change the $^3$He/$^3$H cross-section ratio for this measurement by less than 5\%. If these calculations are correct, then the differences at large missing momenta between the $^3$He/$^3$H experimental and calculated ratios could be due to the underlying $NN$ interaction, and thus could provide new constraints on the previously loosely-constrained short-distance parts of the $NN$ interaction.Comment: 8 pages, 3 figures (4 panels