Inelastic π--p Interactions in the Energy Region of 310 to 454 MeV

Abstract

Differential cross sections for positive pions, protons, and neutrons resulting from inelastic π--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 π+π-n, π0π0n, and π-π0p. 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 π-π scattering lengths; a0=0.65, a1=0.07, and a2=-0.14μ-1. The observed neutron distributions correspond to a strong preference for low c.m.-system neutron energies in both the π+π-n and π0π0n final states. The effect is not present in the observed proton distributions from the π-π0p reaction, which suggests that it is due to a I=0, π-π interaction. The π+ data show the formation of the (3,3) isobar combination of the π--n system in the π+π-n final state. Analysis in terms of an isobar model indicates the predominance of I=1/2 incident state.