Observation of ${\chi }_{cJ}\to 4K_S^0$

By analyzing $(448.1\pm 2.9)\times {10}^6$ $\psi (3686)$ events collected with the BESIII detector operating at the BEPCII collider, the decays of $\chi_{cJ} \to 4K_S^0$($J=0,1,2$) are observed for the first time with statistical significances of 26.5$\sigma$, 5.9$\sigma$ and 11.4$\sigma$, respectively. The product branching fractions of $\psi (3686)\to \gamma {\chi }_{cJ}$, ${\chi }_{cJ}\to 4K_S^0$ are presented and the branching fractions of ${\chi }_{cJ}\to 4K_S^0$ decays are determined to be $$\mathcal{B}${\chi{c0}\to 4K_S^0}$=$(5.76\pm0.34\pm0.38)\times10^{-4}$, $\mathcal{B}_{\chi_{c1}\to 4K_S^0}$=$(0.35\pm0.09\pm0.03)\times10^{-4}$and$$\mathcal{B}${\chi{c2}\to 4K_S^0}$=$(1.14\pm0.15\pm0.08)$$\times {10}^{-4}$, where the first uncertainties are statistical and the second are systematic, respectively.