Search for eta_c decays into pi pi and K Bar K
  Using 58 million $J/\psi$ events taken with the BESII detector, a search for $eta_{c}$ CP violating decays into $\pi\pi$ and $\bar{K}K$ has been performed. No clear $eta_{c}$ is observed, and upper limits for $B(eta_{c}->\pi \pi)$and $B(eta_{c}->\bar{K} K)$ are given at the 90% confidence level, $B(J/\psi->\gamma\eta_{c})\times B(eta_{c}->\pi^{+}\pi^{-})<1.1\times 10^{-5}$ , $B(J/\psi->\gamma\eta_{c})\times B(eta_{c}->\pi^{0}\pi^{0})<0.71\times 10^{-5}$, $B(J/\psi->\gamma\eta_{c})\times B(eta_{c}->K^{+}K^{-})<0.96\times 10^{-5}$ and $B(J/\psi->\gamma\eta_{c})\times B(eta_{c}->{K_{s}}^{0}{K_{s}}^{0})<0.53\times 10^{-5}$. 
M. Ablikim, et al. (BES collaboration)