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 $\chi_{ cJ} \to \Omega^- \bar{ \Omega}^+$ ($J=0,\,1,\,2$) 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 $\mathcal{ B}(\chi_{ c0} \to \Omega^- \bar{ \Omega}^+) = (3.51 \pm 0.54 \pm 0.29) \times 10^{ -5}$, $\mathcal{ B}(\chi_{ c1} \to \Omega^- \bar{ \Omega}^+) = (1.49 \pm 0.23 \pm 0.10) \times 10^{ -5}$, and $\mathcal{ B}(\chi_{ c2} \to \Omega^- \bar{ \Omega}^+) = (4.52 \pm 0.24 \pm 0.18) \times 10^{ -5}$, where the first and second uncertainties are statistical and systematic, respectively.
Categories: hep-ex