Study of the rare decay $J/\ddot{I}ˆ\to \hat{I}{¼}^{+}\hat{I}{¼}^{-}\hat{I}{¼}^{+}\hat{I}{¼}^{-}$

LHCb collaboration, R. Aaij, A. S. W. Abdelmotteleb +1099

The rare electromagnetic $J/\ddot{I}ˆ\to \hat{I}{¼}^{+}\hat{I}{¼}^{-}\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ decay is observed with a significance greatly exceeding the discovery threshold, using proton-proton collision data collected by…