Precise determination of decay rates for ${\eta }_c\to \gamma \gamma$, $J/\psi \to \gamma {\eta }_c$ and $J/\psi \to {\eta }_c{e}^{+}{e}^{-}$ from lattice QCD

Brian Colquhoun, Laurence J. Cooper, Christine T. H. Davies +1

We calculate the decay rates for ${\eta }_c\to \gamma \gamma$, $J/\psi \to \gamma {\eta }_c$ and $J/\psi \to {\eta }_c{e}^{+}{e}^{-}$ in lattice QCD with $u$, $d$, $s$ and $c$ quarks in the sea for the first time. We improve sign…