Observation of the Dalitz Decay $η' \to γe^+e^-$
М. Н. Ачасов, X. Ai, O. Albayrak, M. Albrecht et autres
We report the first observation of the Dalitz decay $η' \to γe^+e^-$, based on a data sample of 1.31 billion $J/ψ$ events collected with the BESIII detector. The $η'$ mesons are produced via the $J/ψ\to γη'$ decay process. The ratio $Γ(η' \to …