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Evidence for the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>η</mml:mi></mml:mrow><mml:mrow><mml:mi>c</mml:mi></mml:mrow></mml:msub><mml:mo stretchy="false">(</mml:mo><mml:mn>2</mml:mn><mml:mi>S</mml:mi><mml:mo stretchy="false">)</mml:mo><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow…
The decay ${\ensuremath{\eta}}_{c}(2S)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\eta}$ is searched for through the radiative transition $\ensuremath{\psi}(3686)\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\eta}}_{c}(2S)$ using 448 million $\ensuremath{\psi}(3686)$ events accumulated at the BESIII detector. The first evidence of ${\ensuremath{\eta}}_{c}(2S)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\eta}$ is found with a statistical significance of $3.5\ensuremath{\sigma}$. The product of the branching fractions of $\ensuremath{\psi}(3686)\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\eta}}_{c}(2S)$ and ${\ensuremath{\eta}}_{c}(2S)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\eta}$ is measured to be $\mathrm{Br}(\ensuremath{\psi}(3686)\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\eta}}_{c}(2S))\ifmmode\times\else\texttimes\fi{}\mathrm{Br}({\ensuremath{\eta}}_{c}(2S)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\eta})=\phantom{\rule{0ex}{0ex}}(2.97\ifmmode\pm\else\textpm\fi{}0.81\ifmmode\pm\else\textpm\fi{}0.26)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, where …