Search for the double Dalitz decays $\eta /{\eta }^{\prime }\to e^{+}{e}^{-}{\mu }^{+}{\mu }^{-}$ and ${\eta }^{\prime }\to {\mu }^{+}{\mu }^{-}{\mu }^{+}{\mu }^{-}$

BESIII Collaboration, M. Ablikim, M. N. Achasov +653

Using a data sample of $(10087\pm 44)\times 10^6$ $J/\psi$ events collected with the BESIII detector, we search for the decays $\eta /{\eta }^{\prime }\to e^{+}{e}^{-}{\mu }^{+}{\mu }^{-}$ and ${\eta }^{\prime }\to {\mu }^{+}{\mu }^{-}{\mu }^{+}{\mu }^{-}$ v…