Three-Body Forces and Neutron-Neutron Effective-Range Parameters

It is suggested that the difference which presently exists between neutron-neutron effective-range parameters extracted from the reactions $\mathrm{D}({\pi }^{-},\gamma )2n$ and $\mathrm{D}(n, 2n)p$ can be explained by the same three-body force which describes ${}_{}{}^3{}_{}{}^{}\mathrm{H}$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. The effects of the three-body force are different for neutron pickup and proton knockon processes in the reaction $\mathrm{D}(n, 2n)p$.