In the presence of strong $\Lambda \mathrm{NN}$ forces, the average potential in which a $\Lambda$ moves is no longer of Woods-Saxon shape. This invalidates the current procedure of estimating the well depth of $\Lambda$ in nuclear matter. This is indicated by the present calculation with the two-pion-exchange $\Lambda \mathrm{NN}$ potential.

• Received 24 October 1968

DOI:https://doi.org/10.1103/PhysRevLett.21.1828