Observation of $\psi \left(3686\right)\to \Lambda \overline{\Lambda }{\eta }^{\prime }$ decay

Using a sample of $\left(27.12±0.14\right)×{10}^{8}\text{}\text{}\psi \left(3686\right)$ events collected with the BESIII detector, the decay $\psi \left(3686\right)\to \Lambda \overline{\Lambda }{\eta }^{\prime }$ with ${\eta }^{\prime }$ subsequently decaying into $\gamma {\pi }^{+}{\pi }^{-}$ and $\eta {\pi }^{+}{\pi }^{-}$ is observed for the first time. The branching fraction of $\psi \left(3686\right)\to \Lambda \overline{\Lambda }{\eta }^{\prime }$ is measured to be $\left(7.34±0.94\left(\mathrm{stat}\right)±0.43\left(\mathrm{sys}\right)\right)×{10}^{-6}$. No resonant structures are evident in the $\Lambda {\eta }^{\prime }$, $\overline{\Lambda }{\eta }^{\prime }$ and $\Lambda \overline{\Lambda }$ mass spectra.