Neutron-NeutronS01Scattering Parameters from a Kinematically Complete Experiment on the ReactionH2(n, 2n)H

In a complete experiment on the reaction ${}_{}{}^2{}_{}{}^{}\mathrm{H}(n, 2n)\mathrm{H}$ we have observed neutron-neutron and neutron-proton final-state interactions. The analysis by a three-body calculation with separable potentials gives $a_{\mathrm{nn}}=-14.5\mathrm{}\pm 0.8$ fm for the ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ neutron-neutron scattering length and ${\mathcal{r}}_m=2.7\mathrm{}\pm 0.5$ fm for the effective range.