Heavy ion collisions and AdS/CFT

We review some recent applications of the AdS/CFT correspondence to heavy ion collisions including a calculation of the jet quenching parameter in N=4 super-Yang-Mills theory and quarkonium suppression from velocity scaling of the screening length for a heavy quark-antiquark pair. We also briefly discuss differences and similarities between QCD and N=4 Super-Yang-Mills theory.Comment: Plenary talk given at Quark Matter 2006, Shanghai, China, 14-20 Nov 2006; to appear in the conference proceedin

Partial Wave Analysis of χc0→π+π−K+K−\chi_{c0}\to\pi^+\pi^-K^+K^-

A partial wave analysis of $\chi_{c0}\to\pi^+\pi^-K^+K^-$ in $\psi(2S)\to\gamma\chi_{c0}$ decay is presented using a sample of 14 million $\psi(2S)$ events accumulated by the BES II detector. The data are fitted to the sum of relativistic covariant tensor amplitudes for intermediate resonant decay modes. From the fit, significant contributions to $\chi_{c0}$ decays from the channels $f_0(980)f_0(980)$, $f_0(980)f_0(2200)$, $f_0(1370)f_0(1710)$, $K^*(892)^0\bar K^*(892)^0$, $K^*_0(1430)\bar K^*_0(1430)$, $K^*_0(1430)\bar K^*_2(1430) + c.c.$, and $K_1(1270)K$ are found. Flavor-SU(3)-violating $K_1(1270)-K_1(1400)$ asymmetry is observed. Values obtained for the masses and widths of the resonances $f_0(1710)$, $f_0(2200)$, $f_0(1370)$, and $K^*_0(1430)$ are presented.Comment: 16 pages, 9 figures, and 4 table

Experimental study of ψ(2S)\psi(2S) decays to \K^+ K^- \pi^+ \pi^- \pi^0 final states

$K^+K^-\pi^+\pi^-\pi^0$ final states are studied using a sample of $14\times10^6$ $\psi(2S)$ decays collected with the Beijing Spectrometer (BESII) at the Beijing Electron-Position Collider. The branching fractions of $\psi(2S)$ decays to $K^+K^-\pi^+\pi^-\pi^0$, $\omega K^+ K^-$, $\omega f_0(1710)$, $K^{\ast}(892)^0 K^- \pi^+\pi^0+c.c.$, $K^{\ast}(892)^{+} K^- \pi^+\pi^- +c.c.$, $K^{\ast}(892)^{+} K^- \rho^0+c.c.$ and $K^{\ast}(892)^0 K^-\rho^+ + c.c.$ are determined. The first two agree with previous measurements, and the last five are first measurements.Comment: 19 pages, 9 figure

Search for psi(3770)\ra\rho\pi at the BESII detector at the Beijing Electron-Positron Collider

Non-$D\bar{D}$ decay \psppto \rhopi is searched for using a data sample of $(17.3\pm 0.5) pb^{-1}$ taken at the center-of-mass energy of 3.773 GeV by the BESII detector at the BEPC. No \rhopi signal is observed, and the upper limit of the cross section is measured to be \sigma(\EETO \rhopi)<6.0 pb at 90% C. L. Considering the interference between the continuum amplitude and the \pspp resonance amplitude, the branching fraction of \pspp decays to $\rho\pi$ is determined to be \BR(\pspp\ra\rho\pi)\in(6.0\times10^{-6}, 2.4\times10^{-3}) at 90% C. L. This is in agreement with the prediction of the $S$- and $D$-wave mixing scheme of the charmonium states for solving the ``\rhopi puzzle'' between \jpsi and \psp decays.Comment: 15 pages, 5 figure

Measurement of the branching fractions of psi(2S) -> 3(pi+pi-) and J/psi -> 2(pi+pi-)

Using data samples collected at sqrt(s) = 3.686GeV and 3.650GeV by the BESII detector at the BEPC, the branching fraction of psi(2S) -> 3(pi+pi-) is measured to be [4.83 +- 0.38(stat) +- 0.69(syst)] x 10^-4, and the relative branching fraction of J/psi -> 2(pi+pi-) to that of J/psi -> mu+mu- is measured to be [5.86 +- 0.19(stat) +- 0.39(syst)]% via psi(2S) -> (pi+pi-)J/psi, J/psi -> 2(pi+pi-). The electromagnetic form factor of 3(pi+pi-) is determined to be 0.21 +- 0.02 and 0.20 +- 0.01 at sqrt(s) = 3.686GeV and 3.650GeV, respectively.Comment: 17pages, 7 figures, submitted to Phys. Rev.

First observation of ψ(2S)→pnˉπ−+c.c.\psi(2S) \to p \bar{n} \pi^- +c.c.

Using 14 million $\psi(2S)$ events collected with the Beijing Spectrometer (BESII) at the Beijing Electron-Positron Collider, the branching fractions of $\psi(2S)$ decays to $p \bar{n} \pi^-$ and $\bar{p} n \pi^+$ and the branching fractions of the main background channels $\psi(2S) \to p \bar{n} \pi^-\pi^0$, $\psi(2S) \to \gamma\chi_{c0} \to \gamma p \bar{n} \pi^-$, $\psi(2S) \to \gamma\chi_{c2} \to \gamma p \bar{n} \pi^-$, and $\psi(2S) \to \gamma \chi_{cJ} \to \gamma p \bar{n} \pi^- \pi^0$ are determined. The contributions of the $N^{\ast}$ resonances in $\psi(2S) \to p \bar{n} \pi^- +c.c.$ are also discussed.Comment: 19 pages, 8 figures, add vertex requirement systematic erro

Observation of a resonance X(1835) in J/\psi --> \gamma \pi^+ \pi^- \eta^{\prime}

The decay channel J/\psi --> \gamma \pi^+ \pi^- \eta^{\prime} is analyzed using a sample of 5.8\times 10^7 J\psi events collected with the BESII detector. A resonance, the X(1835), is observed in the \pi^+ \pi^- \eta^{\prime} invariant mass spectrum with a statistical significance of 7.7 \sigma. A fit with a Breit-Wigner function yields a mass M = 1833.7 \pm 6.1(stat) \pm 2.7(syst) MeV/c^2, a width \Gamma = 67.7 \pm 20.3(stat) \pm 7.7(syst) MeV/c^2 and a product branching fraction B(J/\psi --> \gamma X) B(X --> \pi^+ \pi^- \eta^{\prime}) = (2.2 \pm 0.4(stat) \pm 0.4(syst)) \times 10^{-4}. The mass and width of the X(1835) are not compatible with any known meson resonance. Its properties are consistent with expectations for the state that produces the strong p\bar{p} mass threshold enhancement observed in the J\psi -->\gamma p \bar{p} process at BESII.Comment: 5 pages, 3 figures, RevTex4, Submitted to Phys. Rev. Let

Measurement of \psip Radiative Decays

Using 14 million psi(2S) events accumulated at the BESII detector, we report first measurements of branching fractions or upper limits for psi(2S) decays into gamma ppbar, gamma 2(pi^+pi^-), gamma K_s K^-pi^++c.c., gamma K^+ K^- pi^+pi^-, gamma K^{*0} K^- pi^+ +c.c., gamma K^{*0}\bar K^{*0}, gamma pi^+pi^- p pbar, gamma 2(K^+K^-), gamma 3(pi^+pi^-), and gamma 2(pi^+pi^-)K^+K^- with the invariant mass of hadrons below 2.9GeV/c^2. We also report branching fractions of psi(2S) decays into 2(pi^+pi^-) pi^0, omega pi^+pi^-, omega f_2(1270), b_1^\pm pi^\mp, and pi^0 2(pi^+pi^-) K^+K^-.Comment: 5 pages, 4 figure

Measurements of J/ψJ/\psi and ψ(2S)\psi(2S) decays into ΛΛˉπ0\Lambda \bar{\Lambda}\pi^0 and ΛΛˉη\Lambda \bar{\Lambda}\eta

Using 58 million $J/\psi$ and 14 million $\psi(2S)$ events collected by the BESII detector at the BEPC, branching fractions or upper limits for the decays $J/\psi$ and $\psi(2S) \to \Lambda \bar{\Lambda}\pi^0$ and $\Lambda \bar{\Lambda}\eta$ are measured. For the isospin violating decays, the upper limits are determined to be ${\cal B}(J/\psi \to \Lambda \bar{\Lambda}\pi^0)<6.4\times 10^{-5}$ and ${\cal B}(\psi(2S) \to \Lambda \bar{\Lambda}\pi^0)<4.9\times 10^{-5}$ at the 90% confidence level. The isospin conserving process $J/\psi \to \Lambda \bar{\Lambda}\eta$ is observed for the first time, and its branching fraction is measured to be ${\cal B}(J/\psi \to \Lambda \bar{\Lambda}\eta)=(2.62\pm 0.60\pm 0.44)\times 10^{-4}$, where the first error is statistical and the second one is systematic. No $\Lambda \bar{\Lambda}\eta$ signal is observed in $\psi(2S)$ decays, and ${\cal B}(\psi(2S) \to \Lambda \bar{\Lambda}\eta)<1.2\times 10^{-4}$ is set at the 90% confidence level. Branching fractions of $J/\psi$ decays into $\Sigma^+ \pi^- bar{\Lambda}$ and $\bar{\Sigma}^- \pi^+ \Lambda$ are also reported, and the sum of these branching fractions is determined to be ${\cal B}(J/\psi \to \Sigma^+\pi^- \bar{\Lambda} + c.c.)=(1.52\pm 0.08\pm 0.16)\times 10^{-3}$.Comment: 7 pages, 10 figures. Phys.Rev.D comments considere

Measurements of the continuum RudsR_{\rm uds} and RR values in e+e−e^+e^- annihilation in the energy region between 3.650 and 3.872 GeV

We report measurents of the continuum $R_{\rm uds}$ near the center-of-mass energy of 3.70 GeV, the $R_{{\rm uds(c)}+\psi(3770)}(s)$ and the $R_{\rm had}(s)$ values in $e^+e^-$ annihilation at 68 energy points in the energy region between 3.650 and 3.872 GeV with the BES-II detector at the BEPC Collodier. We obtain the $R_{\rm uds}$ for the continuum light hadron (containing u, d and s quarks) production near the $D\bar D$ threshold to be $R_{\rm uds}=2.141 \pm 0.025 \pm 0.085$.Comment: 5 pages, 3 figure