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.Comment: 6 pages, 3figure

Direct Measurements of the Branching Fractions for the Semileptonic Decays D0→K−μ+νμD^0 \to K^-\mu^+\nu_\mu and D0→π−μ+νμD^0 \to \pi^-\mu^+\nu_\mu

Based on the data sample of 33 pb$^{-1}$ collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, the absolute branching fractions for the semileptonic decays $D^0\to K^-\mu^+\nu_\mu$ and $D^0\to\pi^-\mu^+\nu_\mu$ have been measured. In the system recoiling against $7584\pm198\pm341$ singly tagged $\bar D^0$ mesons, $87.2\pm13.6$ events for $D^0\to K^-\mu^+\nu_\mu$ and $9.3\pm7.4$ events for $D^0\to\pi^-\mu^+\nu_\mu$ are observed. These yield the absolute branching fractions to be $BF(D^0\to K^-\mu ^+\nu_\mu)= (3.55\pm0.56\pm0.59)$ and $BF(D^0\to\pi^-\mu^+\nu_\mu)= (0.38\pm0.30\pm0.10)$. The measured branching fraction for $D^0\to K^-\mu ^+\nu_\mu$ was previously used to determine the ratio $\Gamma(D^0\to K^-\mu^+\nu_\mu)/ \Gamma(D^+\to \bar K^0\mu^+\nu_\mu)$ combining the previously measured branching fraction for $D^+\to \bar K^0\mu^+\nu_\mu$ by the BES Collaboration.Comment: 7 pages, 6 figure

psi(2S) Radiative Decay Measurements

Using a sample of 14 million \psip events collected with the BESII detector, branching fractions or upper limits on the branching fractions of \psip decays into \gamma\ppb, \gamma 2(\pip\pim), \gamma \kskp, \gamma \kap\kam\pip\pim, \gamma\kstarz\kam\pip+c.c., \gamma \kstarz \kstarzb, \gamma\pip\pim\ppb, \gamma2(\kap\kam), \gamma3(\pip\pim) and \gamma2(\pip\pim)\kap\kam with hadron invariant mass less than 2.9\gev/c^2 are reported. We also report branching fractions of \psip decays into \gamma\ppb\piz, \ppb\piz\piz, 2(\pip\pim)\piz, \omega\pp, $\omega f_2(1270)$, $b_1^\pm\pi^\mp$, \piz\kskp, K^\pm\rho^\mp\ks, \piz2(\pip\pim)\kap\kam and \gamma\piz2(\pip\pim)\kap\kam.Comment: 14 pages, 20 figures, one number error is correcte

Charmonium Decays to Axialvector plus Pseudoscalar Mesons

A sample of 3.79 million psi(2S) decays observed in the BES detector is used to study the decays of charmonium to axialvector plus pseudoscalar mesons. The branching fraction for psi(2S) to b1pi agrees with expectations. A contrasting behavior between the psi(2S) and the J/psi decays to K1K cannot be accommodated by an adjustment of the singlet-triplet axialvector mixing angle.Comment: 7 pages, 3 figures. Changes: excluded one figure, added information, systematic errors increase

Light Hadrons and New Enhancements in J/ψ\psi Decays at BESII

Based on 58 million $J/\psi$ samples collected by the BESII detector at the BEPC, many mesons, baryons, and new resonances have been reported. Here, I will review some recent results of glueball candidates and new enhancement.Comment: 6 pages, 7 figures, Rencontres de Moriond EW 200

First Evidence of Lambda Lambda-bar in \chi_cJ Decays

The first observation of \chi_cJ (J=0,1,2) decays to Lambda Lambda-bar is reported using \psi(2S) data collected with the BESII detector at the BEPC. The branching ratios are determined to be BR(\chi_c0 \to Lambda Lambda-bar) = (4.7^{+1.3}_{-1.2} \pm 1.0)\times 10^{-4}, BR(\chi_c1 \to Lambda Lambda-bar) = (2.6^{+1.0}_{-0.9} \pm 0.6)\times 10^{-4} and BR(\chi_c2 \to Lambda Lambda-bar) = (3.3^{+1.5}_{-1.3} \pm 0.7)\times 10^{-4}. Results are compared with model predictions.Comment: 18 pages, 8 figures, submitted to Phys. Rev.

Study of ψ(2S)\psi(2S) decays into γK+K−\gamma K^+K^- and γπ+π−\gamma \pi^+\pi^-

Radiative charmonium decays from the BESII sample of 14$\times10^{6}$ $\psi(2S)$-events into two different final states, $\gamma K^+K^-$ and $\gamma\pi^+\pi^-$, are analyzed. Product branching fractions for $\psi(2S)\to\gamma X\to \gamma\pi^+\pi^-$, $\gamma K^+K^-$ are given, where $X=f_2(1270)$, $f_0(1500)$, and $f_0(1710)$ in $\pi^+\pi^-$ and $f_2(1270)$, $f_2'(1525)$, and $f_0(1700)$ in $K^+K^-$. An angular analysis gives the ratios of the helicity projections for the $f_2(1270)$ in $\psi(2S)\to\gamma f_2(1270)\to\gamma\pi^+\pi^-$.Comment: 9 pages, 5 figure

Recent Results on ψ(3770)\psi(3770) Physics at BES

There are about 33, 6.5 and 1.0 pb$^{-1}$ of $e^+e^-$ annihilation data have been taken around the center-of-mass energies of $\sqrt s=$ 3.773 GeV, at $\sqrt s=$ 3.650 GeV and at $\sqrt s=$ 3.6648 GeV, respectively, with the BES-II detector at the BEPC collider. By analyzing these data sets, we have measured the branching fraction for $\psi(3770)\to$ non-$D\bar D$ by several different methods; and have observed an anomalous line shape of $\sigma^{e^+e^-\to{\rm hadrons}}$ in energy region from 3.65 to 3.87 GeV; and have measured the line shapes of the $D^+D^-$, $D^0\bar D^0$ and $D\bar D$ production and together with the ratios of the production rates of $D^+D^-$ and $D^0\bar D^0$ in $e^+e^-$ annihilation around the $\psi(3770)$ resonance.Comment: 4 pages, 0 figures, to appear in the proceedings of 44th Rencontres de Moriond on QCD and High Energy interactions, La Thuile, Aosta Valley, Italy, 14-21 March 200

Evidence of σ\sigma particle in J/ψ→ωππJ/\psi \to \omega \pi \pi

Based on a sample of 7.8 million BESI $J/\psi$ events, the decay of $J/\psi \to \omega \pi^+ \pi^-$ is studied. A low mass enhancement in the $\pi^+ \pi^-$ invariant mass spectrum recoiling against $\omega$ particle is clearly seen which does not come from the phase space effect and the background. According to PWA analysis, this low mass enhancement is a broad $0^{++}$ resonance, the $\sigma$ particle. If a Breit-Winger function of constant width is used to fit the $\sigma$ signal, its mass and width are $384 \pm 66$ MeV and $458 \pm 100$ MeV respectively, which correspond to the pole position at (434 $\pm$ 78) - $i$ (202 $\pm$ 43) MeV.Comment: 7 pages, 7 figure

New R Values in 2-5 Gev from the Beijing Spectrometer

The values of $R = \sigma(e^+e^-\to {hadrons})/\sigma(e^+e^-\to\mu^+\mu^-)$ for 85 center-of-mass energies between 2 and 5 GeV were measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider, with an average uncertainty of $\sim7$.Comment: 4 pages, 1 figure, 1 table, talk given at XXXVIth Rencontres de Moriond, Electroweak Interactions and Unified Theories, Les Arcs, Savoie, France, March 10-17 200