Contribution of Nucleon-Nucleon $\mathit{P}$ Waves to $\mathit{nt}-\mathit{nt}$, $\mathit{dd}-\mathit{pt}$, and $\mathit{dd}-\mathit{dd}$ Scattering Observables

The four-body equations of Alt, Grassberger, and Sandhas [Phys. Rev. C 1, 85 (1970)] are solved for a system of four nucleons, using realistic NN interactions in channels $j\le 2$. The results of the calculation are compared with data for the reactions $\mathrm{dd}\to \mathrm{dd}$, $\mathrm{dd}\to p^3\mathrm{H}$, and $n^3\mathrm{H}\to n^3\mathrm{H}$. The calculations indicate that the NN P waves have a strong effect on 4N observables including a $10\%$ contribution to the total $n^3\mathrm{H}\to n^3\mathrm{H}$ cross section at the peak of the low energy resonance.