Evidence for ${\eta }_c\to \gamma \gamma$ and Measurement of $J/\psi \to 3\gamma$

BESIII Collaboration, M. Ablikim, M. N. Achasov +340

The decay of $J/\psi$ to three photons is studied using $\psi (3686)\to {\pi }^{+}{\pi }^{-}J/\psi$ in a sample of $1.0641\times 10^8$ $\psi (3686)$ events collected with the BESIII detector. Evidence of the di…