Evidence for ${\eta }_c$(2S)$\to$\pipieta decay

The decay ${\eta }_c(2S)\to$\pipieta is searched for through the radiative transition $\psi (3686)\to \gamma {\eta }_c(2S)$ using 448 million $\psi$(3686) events accumulated at the BESIII detector. The first evidence of ${\eta }_c(2S)\to {\pi }^{+}{\pi }^{-}\eta$ is found with a statistical significance of 3.5$\sigma$. The product of the branching fractions of $\psi (3686)\to \gamma {\eta }_c(2S)$ and ${\eta }_c(2S)\to$\pipieta is measured to be $Br(\psi (3686)\to \gamma {\eta }_c(2S))\times Br({\eta }_c(2S)\to$\pipieta$)=(2.97\pm 0.81\pm 0.26)\times {10}^{-6}$, where the first uncertainty is statistical and the second one is systematic. The branching fraction of the decay ${\eta }_c(2S)\to$\pipieta is determined to be $Br({\eta }_c(2S)\to$\pipieta$)=(42.4\pm 11.6\pm 3.8\pm 30.3)\times {10}^{-4}$, where the third uncertainty is transferred from the uncertainty of the branching fraction of $\psi (3686)\to \gamma {\eta }_c(2S)$.