Measurement of the double Dalitz decay $\eta \to e^{+}{e}^{-}{e}^{+}{e}^{-}$

BESIII Collaboration, M. Ablikim, M. N. Achasov +689

Using a data sample of $(1.0087\pm 0.0044)\times 10^{10}$ $J/\psi$ events collected with the BESIII detector, we study the rare double Dalitz decay of $\eta \to e^{+}{e}^{-}{e}^{+}{e}^{-}$…