Using a sample of $448.1\times {10}^6\psi (3686)$ events collected with the BESIII detector in 2009 and 2012, we study the decays ${\chi }_{c0,2}\to {\eta }^{\prime }{\eta }^{\prime }$ and $\eta {\eta }^{\prime }$. The decays ${\chi }_{c2}\to {\eta }^{\prime }{\eta }^{\prime }$, ${\chi }_{c0}\to \eta {\eta }^{\prime }$ and ${\chi }_{c2}\to \eta {\eta }^{\prime }$ are observed for the first time with statistical significances of $9.6\sigma$, $13.4\sigma$ and $7.5\sigma$, respectively. The branching fractions are determined to be $\mathcal{B}({\chi }_{c0}\to {\eta }^{\prime }{\eta }^{\prime })=(2.19\pm 0.03\pm 0.14)\times {10}^{-3}$, $\mathcal{B}({\chi }_{c2}\to {\eta }^{\prime }{\eta }^{\prime })=(4.76\pm 0.56\pm 0.38)\times {10}^{-5}$, $\mathcal{B}({\chi }_{c0}\to \eta {\eta }^{\prime })=(8.92\pm 0.84\pm 0.65)\times {10}^{-5}$ and $\mathcal{B}({\chi }_{c2}\to \eta {\eta }^{\prime })=(2.27\pm 0.43\pm 0.25)\times {10}^{-5}$, where the first uncertainties are statistical and the second are systematic. The precision for the measurement of $\mathcal{B}({\chi }_{c0}\to {\eta }^{\prime }{\eta }^{\prime })$ is significantly improved compared to previous measurements. Based on the measured branching fractions, the role played by the doubly and singly Okubo-Zweig-Iizuka disconnected transition amplitudes for ${\chi }_{c0,2}$ decays into pseudoscalar meson pairs can be clarified.

• Received 25 July 2017

DOI:https://doi.org/10.1103/PhysRevD.96.112006