The decays $J/\psi \to \eta {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}$ and $\psi (3686)\to \eta {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}$ are observed for the first time, using $(10087\pm 44)\times {10}^{6}J/\psi$ and $(448.1\pm 2.9)\times {10}^6\psi (3686)$ events collected with the BESIII detector at the BEPCII collider. We determine the branching fractions of these two decays to be $\mathcal{B}(J/\psi \to \eta {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-})=(6.34\pm 0.21\pm 0.37)\times {10}^{-5}$ and $\mathcal{B}(\psi (3686)\to \eta {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-})=(9.59\pm 2.37\pm 0.61)\times {10}^{-6}$, where the first uncertainties are statistical and the second are systematic. The ratio of these two branching fractions is determined to be $\frac{\mathcal{B}(\psi (3686)\to \eta {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-})}{\mathcal{B}(J/\psi \to \eta {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-})}=(15.1\pm 3.8)\%$, which is in agreement with the “12% rule.”

• Received 19 October 2022
• Accepted 28 November 2022
• Corrected 4 April 2024

DOI:https://doi.org/10.1103/PhysRevD.106.112007

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Published by the American Physical Society