Measurements of the observed cross sections for e+e−→e^+e^-\to exclusive light hadrons containing π0π0\pi^0\pi^0 at s=3.773\sqrt s= 3.773, 3.650 and 3.6648 GeV

By analyzing the data sets of 17.3, 6.5 and 1.0 pb$^{-1}$ taken, respectively, at $\sqrt s= 3.773$, 3.650 and 3.6648 GeV with the BES-II detector at the BEPC collider, we measure the observed cross sections for $e^+e^-\to \pi^+\pi^-\pi^0\pi^0$, $K^+K^-\pi^0\pi^0$, $2(\pi^+\pi^-\pi^0)$, $K^+K^-\pi^+\pi^-\pi^0\pi^0$ and $3(\pi^+\pi^-)\pi^0\pi^0$ at the three energy points. Based on these cross sections we set the upper limits on the observed cross sections and the branching fractions for $\psi(3770)$ decay into these final states at 90% C.L..Comment: 7 pages, 2 figure

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

A precision determination of the mass of the η\eta meson

Several processes of meson production in proton-deuteron collisions have been measured simultaneously using a calibrated magnetic spectrograph. Among these processes, the $\eta$ meson is seen clearly as a sharp missing--mass peak on a slowly varying background in the $p+d\to ^3\textrm{He} +X$ reaction. Knowing the kinematics of the other reactions with well determined masses, it is possible to deduce a precise mass for the $\eta$ meson. The final result, $m(\eta)=547.311\pm 0.028 \textrm{(stat)} \pm 0.032 \textrm{(syst) MeV/c}^2$, is significantly lower than that found by the recent NA48 measurement, though it is consistent with values obtained in earlier counter experiments.Comment: 10 pages, 6 figures, Fig. 3 change

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

Future Physics Programme of BESIII

International audienceThere has recently been a dramatic renewal of interest in hadron spectroscopy and charm physics. This renaissance has been driven in part by the discovery of a plethora of charmonium-like XYZ states at BESIII and B factories, and the observation of an intriguing proton-antiproton threshold enhancement and the possibly related X(1835) meson state at BESIII, as well as the threshold measurements of charm mesons and charm baryons. We present a detailed survey of the important topics in tau-charm physics and hadron physics that can be further explored at BESIII during the remaining operation period of BEPCII. This survey will help in the optimization of the data-taking plan over the coming years, and provides physics motivation for the possible upgrade of BEPCII to higher luminosity