Pion-Production Amplitudes and Nucleon-Nucleon Interaction

The present knowledge of the partial-wave proton-proton absorptions due to pion production below 1.5 GeV of laboratory kinetic energy is summarized. The three models which have been used for obtaining this kind of information from inelastic data are discussed: the Mandelstam model, the one-pion-exchange model, and the $K$ matrix, or damping, model. Although there is some disagreement, in the near future one can hope to obtain reasonably trustworthy values for partial wave absorptions as a function of energy from the threshold of pion production to about 1.5 GeV. This information will be useful not only to reduce the number of parameters in high-energy phase-shift analysis, but also to be introduced as known inelasticities in partial wave dispersion relations.