Observation of $eta^{prime}toomega e^{+} e^{-}$

Based on a sample of etapr mesons produced in the radiative decay $J/psitogammaeta^{prime}$ in $1.31times 10^9$ $J/psi$ events collected with the BESIII detector, the decay $eta^{prime}toomega e^{+} e^{-}$ is observed for the first time, with a statistical significance of $8sigma$. The branching fraction is measured to be $mathcal{B}(eta^{prime}toomega e^{+} e^{-})=(1.97pm0.34(text{stat})pm0.17(text{syst}))times10^{-4}$, which is in agreement with theoretical predictions. The branching fraction of $eta^{prime}toomegagamma$ is also measured to be $(2.55pm0.03(text{stat})pm0.16(text{syst}))times10^{-2}$, which is the most precise measurement to date, and the relative branching fraction $frac{mathcal{B}(eta^{prime}to omega e^{+}e^{-})}{mathcal{B}(eta^{prime}to omega gamma)}$ is determined to be $(7.71pm1.34(text{stat})pm0.54(text{syst}))times10^{-3}$.