SINGLE $pi$$sup -$ PRODUCTION IN n-p COLLISIONS NEAR THRESHOLD

Abstract : Over 4000 n+ p to pion (-) +p+p events, obtained in a hydrogen bubble chamber, were analyzed. The kinetic energies of the initiating neutrons ranged from threshold to 440 MeV. The angular distributions, correlations, and energy partition of the final-state particles as well as the excitation function are presented. They are in excellent agreement with the phenomenological theory of Gell-Mann and Watson, except for the absence in the data of a sharp peak in the momentum partition distribution near the maximum allowed pion (-) momentum. The Ps amplitudes account for less than 1% of the total cross section. The intensities of the various types of transitions are determined. Examples of sets of amplitudes which yield these intensities are given. However, a large number of amplitudes contribute to the cross section, and the ambiguities are too great to allow evaluation of individual amplitudes. (Author)