Study of the decays ${\chi }_{cJ}\to \mathrm{\Lambda }\bar{\mathrm{\Lambda }}\phi$

Based on $(2712.4\pm 14.3)\times {10}^6$ $e^{+}{e}^{-}\to \psi (3686)$ events collected with the BESIII detector operating at the BEPCII collider, we report the first evidence of ${\chi }_{c0}\to \mathrm{\Lambda }\bar{\mathrm{\Lambda }}\phi$ decays and the first observation of ${\chi }_{c1,2}\to \mathrm{\Lambda }\bar{\mathrm{\Lambda }}\phi$ decays, with significances of $4.5\sigma$, $11.3\sigma$ and $13.0\sigma$, respectively. The decay branching fractions of ${\chi }_{c0,1,2}\to \mathrm{\Lambda }\bar{\mathrm{\Lambda }}\phi$ are measured to be $(2.99\pm 1.24\pm 0.19)\times {10}^{-5}$, $(6.01\pm 0.90\pm 0.40)\times {10}^{-5}$, and $(7.13\pm 0.81\pm 0.36)\times {10}^{-5}$, where the first uncertainties are statistical and the second systematic. No obvious enhancement near the $\mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ production threshold or excited $\mathrm{\Lambda }$ state is found in the $\mathrm{\Lambda }\phi$ (or $\bar{\mathrm{\Lambda }}\phi$) system.