$\mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ final-state interaction in the reactions $e^{+}{e}^{-}\to \phi \mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ and $e^{+}{e}^{-}\to \eta \mathrm{\Lambda }\bar{\mathrm{\Lambda }}$

Near-threshold $\mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ mass spectra for the reactions $e^{+}{e}^{-}\to \eta \mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ and $e^{+}{e}^{-}\to \phi \mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ are investigated with an emphasis on the role played by the interaction in the $\mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ system. A variety of $\mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ potential models is employed that have been established in the analysis of data on $p\bar{p}\to \mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ in the past. It is shown that the near-threshold enhancement observed for the two $e^{+}{e}^{-}$ reactions can be reproduced by considering the $\mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ final-state interaction in the partial waves suggested by the helicity-angle analysis of the experiments. For $e^{+}{e}^{-}\to \eta \mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ the same $\mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ $S$-wave interaction as in $e^{+}{e}^{-}\to \mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ is relevant and with it a consistent description of the pertinent measurements can be achieved. It is pointed out that a nonzero threshold cross section as observed for the latter reaction is not supported by the new $\eta \mathrm{\Lambda }\bar{\mathrm{\Lambda }}$ data.