First measurement of $e^{+}{e}^{-}\to p{K}_S^0\bar{n}{K}^{-}+c\mathrm{.}c\mathrm{.}$ above open charm threshold

The process $e^{+}{e}^{-}\to p{K}_S^0\bar{n}{K}^{-}+c\mathrm{.}c\mathrm{.}$ and its intermediate processes are studied for the first time, using data samples collected with the BESIII detector at BEPCII at center-of-mass energies of 3.773, 4.008, 4.226, 4.258, 4.358, 4.416, and 4.600 GeV, with a total integrated luminosity of 7.4 fb${}^{-1}$. The Born cross section of $e^+e^- \to p K^{0}_S\bar{n}K^- + c.c.$ is measured at each center-of-mass energy, but no significant resonant structure in the measured cross-section line shape between 3.773 and 4.600 GeV is observed. No evident structure is detected in the $p{K}^{-}$, $n{K}_S^0$, $p{K}_S^0$, $n{K}^{+}$, $p\bar{n}$, or $K_S^0{K}^{-}$ invariant mass distributions except for $\mathrm{\Lambda }(1520)$. The Born cross sections of $e^{+}{e}^{-}\to \mathrm{\Lambda }(1520)\bar{n}{K}_S^0+c\mathrm{.}c\mathrm{.}$ and $e^+e^-\rightarrow \Lambda(1520)\bar{p}K^{+} + c.c.$ are measured, and the 90% confidence level upper limits on the Born cross sections of $e^{+}{e}^{-}\to \mathrm{\Lambda }(1520)\bar{\mathrm{\Lambda }}(1520)$ are determined at the seven center-of-mass energies.