Recent BES charmonium results

Abstract

Using 58 million $J/ψ$ decays, we have investigated the $p \bar{p}$ invariant mass spectrum in the radiative decay $J/ψ\to γp \bar{p}$ and observe a prominent structure with mass near $2m_p$. Fitting with an S-wave Breit-Wigner, we obtain a peak mass of $M= 1859^{+3}_{-10}(\rm stat)^{+5}_{-25}(sys) MeV/c^2$. $J/ψ\to γη_c$ decays from the same sample are used to determine the mass, width, and hadronic branching ratios of the $η_c$. From a sample of 14 million $ψ(2S)$ events, the first observation of $χ_{cJ}$ (J=0,1,2) decays to $Λ\barΛ$ is made, and branching ratios are determined, which are larger than expected from the Color Octet Model. Branching ratios of $K_s^0K_L^0$ in both $ψ(2S)$ and $J/ψ$ decays are measured, and a more than four sigma deviation from the pQCD predicted "12% rule" is observed. In $ψ(3770)$ decays, evidence for the non-$D\bar{D}$ decay to $π^+π^-J/ψ$ is observed.