A new $G$-parity violating amplitude in the $J/\psi$ decay?

R. Baldini Ferroli, F. De Mori, M. Destefanis +25

The $J/\psi$ meson has negative $G$-parity so that, in the limit of isospin conservation, its decay into ${\pi }^{+}{\pi }^{-}$ should be purely electromagnetic. However, the measured branching fra…