Search for the non-$D\overline{D}$ decay $\psi (3770)\to K_S^0{K}_L^0$

Using the current world’s largest data sample of $\psi (3770)$ decays, we present results of a search for the non-$D\overline{D}$ decay $\psi (3770)\to K_S^0{K}_L^0$. We find no signal, and obtain an upper limit of $\sigma (e^{+}{e}^{-}\to \psi (3770)\to K_S^0{K}_L^0)<0.07\mathrm{pb}$ at 90% confidence level (CL). Our result tests a theoretical prediction for the upper bound on $\mathcal{B}(\psi (3770)\to K_S^0{K}_L^0)$ based on a charmonia-mixing model.

Figure 1

The scaled $K_S^0$ energy ($E_{K_S^0}/E_{\mathrm{beam}}$) distribution for the $\psi (3770)$ simulation samples corresponding to the signal (solid histogram) and radiative return (dotted histogram) processes using arbitrary normalization. The arrows mark the signal region.

Figure 2

The scaled $K_S^0$ energy ($E_{K_S^0}/E_{\mathrm{beam}}$) distribution for the $\psi (3770)\to K_S^0{K}_L^0$ decay in $281{\mathrm{pb}}^{-1}$ of data. The arrows mark the signal region.