Radiative and leptonic decays of the pseudoscalar charmonium state ${\eta }_c$

Mao-Zhi Yang

The radiative and leptonic decays of ${\eta }_c\to \gamma \gamma$ and ${\eta }_c\to l^{+}{l}^{-}$ are studied. For ${\eta }_c\to \gamma \gamma$ decay, the second-order electromagnetic tree-level diagram gives the leading contr…