Inelastic ${\pi }^{-}-p$ Interactions in the Energy Region of 310 to 454 MeV

Differential cross sections for positive pions, protons, and neutrons resulting from inelastic ${\pi }^{-}-p$ collisions have been measured from 310- to 454-MeV incident-pion kinetic energy. The data were obtained with electronic counter systems, which measured the energy distribution of the final-state particle of interest at a series of fixed angles. The results have been interpreted in terms of the final states ${\pi }^{+}{\pi }^{-}n$, ${\pi }^0{\pi }^{0}n$, and ${\pi }^{-}{\pi }^{0}p$. The total cross sections for these three modes as a function of incident pion energy are in qualitative agreement with the predictions by Schnitzer. A preference is shown for his set of $\pi -\pi$ scattering lengths; $a_0=0.65\mathrm{}$, $a_1=0.07\mathrm{}$, and $a_2=-0.14\mathrm{}{\mu }^{-1\mathrm{}}$. The observed neutron distributions correspond to a strong preference for low c.m.-system neutron energies in both the ${\pi }^{+}{\pi }^{-}n$ and ${\pi }^0{\pi }^{0}n$ final states. The effect is not present in the observed proton distributions from the ${\pi }^{-}{\pi }^{0}p$ reaction, which suggests that it is due to a $I=0\mathrm{}$, $\pi -\pi$ interaction. The ${\pi }^{+}$ data show the formation of the (3,3) isobar combination of the ${\pi }^{-}-n$ system in the ${\pi }^{+}{\pi }^{-}n$ final state. Analysis in terms of an isobar model indicates the predominance of $I=\frac{1}{2}$ incident state.