Observation of ${\chi }_{cJ}\to 3K_S^0{K}^{\pm }{\pi }^{\mp }$

By analyzing $(2712.4\pm 14.3)\times {10}^6$ $\psi (3686)$ events collected with the BESIII detector operating at the BEPCII collider, the decays ${\chi }_{c0,1,2}\to 3K_S^0{K}^{\pm }{\pi }^{\mp }$ are observed for the first time with statistical significances greater than $10\sigma$. The branching fractions of these decays are determined to be $\mathcal{B}({\chi }_{c0}\to 3K_S^0{K}^{\pm }{\pi }^{\mp })=(7.95\pm 0.50\pm 0.65)\times {10}^{-5},$ $\mathcal{B}({\chi }_{c1}\to 3K_S^0{K}^{\pm }{\pi }^{\mp })=(2.62\pm 0.08\pm 0.19)\times {10}^{-4},$ and $\mathcal{B}({\chi }_{c2}\to 3K_S^0{K}^{\pm }{\pi }^{\mp })=(1.72\pm 0.07\pm 0.15)\times {10}^{-4},$ where the first uncertainties are statistical and the second systematic.