\begin{document}${ \Xi^- t} $\end{document} quasibound state instead of ΛΛ nn bound state

The coupled \begin{document}$ \Lambda\Lambda nn-\Xi^- pnn $\end{document} system was studied to investigate whether the inclusion of channel coupling is able to bind the \begin{document}$ \Lambda\Lambda nn $\end{document} system. We use a separable potential three-body model of the coupled \begin{document}$ \Lambda\Lambda nn - \Xi^- pnn $\end{document} system and a variational four-body calculation with realistic interactions. Our results exclude the possibility of a \begin{document}$ \Lambda\Lambda nn $\end{document} bound state by a large margin. Instead, we found a \begin{document}$ \Xi^- t $\end{document} quasibound state above the \begin{document}$ \Lambda\Lambda nn $\end{document} threshold.