Pion Production and the One-Particle-Exchange Mechanism inp¯−pInteractions at3−4 BeVc

Abstract

A study of antiproton-proton collisions at $3-4 \frac{\mathrm{BeV}}{c}$ indicates that about 25% (19 mb) of the total interaction cross section can be attributed to pion production without annihilation. The two outstanding characteristics of the pion-production channels are the strong forward peaking of the antibaryons in the center-of-mass system, and the prominence of the well-known $T=J=\frac{3}{2}$ pion-nucleon resonance $N^{*}\mathrm{}\left(1238\right)\mathrm{}$ and of its antiparticle in the final states. The cross section for the reaction $\overline{p}+p\to \overline{p}+p+{\pi }^{+}+{\pi }^{-}$ is 3.43±0.23 mb at $3.28 \frac{\mathrm{BeV}}{c}$ and 3.67±0.30 mb at $3.66 \frac{\mathrm{BeV}}{c}$. This reaction, which is the major channel contributing to the pion-production cross section, is found to be consistent with a one-pion-exchange mechanism. In particular, the theory of Selleri and Ferrari gives a good fit to many aspects of the data. However, a detailed analysis indicates that pion production in proton-antiproton collisions is not totally consistent with a simple one-pion-exchange mechanism.