A new decay mode of higher charmonium

We calculate the ${\mathrm{\Lambda }}_c{\bar{\mathrm{\Lambda }}}_c$ partial decay width of the excited vector charmonium states around 4.6 GeV with the quark pair creation model. We find that the partial decay width of the ${\mathrm{\Lambda }}_c{\bar{\mathrm{\Lambda }}}_c$ mode can reach up to several MeV for $\psi (4S,5S,6S)$. In contrast, the partial ${\mathrm{\Lambda }}_c{\bar{\mathrm{\Lambda }}}_c$ decay width of the states $\psi (3D,4D,5D)$ is less than one MeV. If the enhancement $Y(4630)$ reported by the Belle Collaboration in ${\mathrm{\Lambda }}_c{\bar{\mathrm{\Lambda }}}_c$ invariant-mass distribution is the same structure as $Y(4660)$, the $Y(4660)$ resonance is most likely to be a $S$-wave charmonium state.