Observation of the decay ${\chi }_{cJ}\to {\mathrm{\Omega }}^{-}{\bar{\mathrm{\Omega }}}^{+}$

Using an $e^{+}{e}^{-}$ collision data sample of $(27.08\pm 0.14)\times {10}^8$ $\psi (3686)$ events collected by the BESIII detector, we report the first observation of ${\chi }_{cJ}\to {\mathrm{\Omega }}^{-}{\bar{\mathrm{\Omega }}}^{+}$ ($J=0,1,2$) decays with significances of $5.6\sigma$, $6.4\sigma$, and $18\sigma$, respectively, where the ${\chi }_{cJ}$ mesons are produced in the radiative $\psi (3686)$ decays. The branching fractions are determined to be $\mathcal{B}({\chi }_{c0}\to {\mathrm{\Omega }}^{-}{\bar{\mathrm{\Omega }}}^{+})=(3.51\pm 0.54\pm 0.29)\times {10}^{-5}$, $\mathcal{B}({\chi }_{c1}\to {\mathrm{\Omega }}^{-}{\bar{\mathrm{\Omega }}}^{+})=(1.49\pm 0.23\pm 0.10)\times {10}^{-5}$, and $\mathcal{B}({\chi }_{c2}\to {\mathrm{\Omega }}^{-}{\bar{\mathrm{\Omega }}}^{+})=(4.52\pm 0.24\pm 0.18)\times {10}^{-5}$, where the first and second uncertainties are statistical and systematic, respectively.