Study of $J\mathrm{/}\psi$ and $\psi (3686)$ decay to $\mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ and ${\mathrm{\Sigma }}^0{\bar{\mathrm{\Sigma }}}^0$ final states

Using $1310.6\times {10}^6$ $J\mathrm{/}\psi$ and $447.9\times {10}^6$ $\psi (3686)$ events collected with the BESIII detector at the BEPCII $e^{+}{e}^{-}$ collider, the branching fractions and the angular distributions of $J\mathrm{/}\psi$ and $\psi (3686)$ decays to $\mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ and ${\mathrm{\Sigma }}^0{\bar{\mathrm{\Sigma }}}^0$ final states are measured. The branching fractions are in agreement with, and much more precise than, the averages of previously published results. The polar angular distributions of $\psi (3686)$ decays are measured for the first time, while those of $J\mathrm{/}\psi$ decays are measured with much improved precision. In addition, the ratios of branching fractions $\frac{\mathcal{B}(\psi (3686)\to \mathrm{\Lambda }\bar{\mathrm{\Lambda }})}{\mathcal{B}(J\mathrm{/}\psi \to \mathrm{\Lambda }\bar{\mathrm{\Lambda }})}$ and $\frac{\mathcal{B}(\psi (3686)\to {\mathrm{\Sigma }}^0{\bar{\mathrm{\Sigma }}}^0)}{\mathcal{B}(J\mathrm{/}\psi \to {\mathrm{\Sigma }}^0{\bar{\mathrm{\Sigma }}}^0)}$ are determined to test the “12% rule”.