A Measurement of the Mass and Full-Width of the ${\eta }_c$ Meson

J. Z. Bai

In a sample of 7.8 million $J/\psi$ decays collected in the Beijing Spectrometer, the process J/$\psi \to \gamma {\eta }_c$ is observed for five different ${\eta }_c$ decay channels: $K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}$, $π^+π^-…