A two-component model definition of two-body nucleon diffraction dissociation in πp→π(Nπ) reactions at 3.9 GeV/c and comparisons with other experiments

Four low-mass 'diffractive like' reactions π+-p→π+-(pπ0) and π+-p→π+-(nπ+) have been studied at 3.9 GeV/c incident pion momentum. These channels have been studied in the framework of a two-component model and a definition of the diffraction dissociation amplitude is proposed. The following three features of the data are discussed: (1) an apparent violation of the predictions of isospin invariance for the cross section ratios, (2) the marked anisotropy of the s-channel helicity distributions and (3) the absence of the cross-over effect in the differential cross sections. The predictions of a two-component model previously used to explain the low mass I=1/2(Nπ) enhancement and s- and t-channel helicity non-conservation are seen to be in agreement with these observations. Predictions are also made for higher energy incident pions and incident K, p, and anti p projectiles. These predictions are compared with available data including recent results at Fermilab and ISR energies. (Auth.)