Present status of the theory of πNN systems

In the present discussion the existing data are compared with various model calculations within the πNN theory to assess the appropriateness of the latter. Globally the models as their present form reproduce the data quite well in view πd and NN channels in which the comparison was made. From the quantitative point of view the models must be upgraded in several different ingredients. First it is the parameters of the NN heavy meson exchange potentials when combined with the explicit pion and nucleon isobar degrees of freedom. A right choice of their values will lead to a better account of such observables like the beam asymmetries and vector analysing power in a number of channels like NN → πd, NN → πNN etc. The next one may be the model for the Δ resonance. In view of the fact that dσ/dω for the deuteron photodisintegration in the Δ resonance region cannot be explained at all by the coupled NN-NΔ model. The third one is also related to the Δ resonance but the possible association could presumably be less. The model deficiency in the πd dσ/dω and it was corrected by introducing an extra (supposedly short ranged) NΔ interaction in the dominant 5S2 and 5P3 waves. This extra interaction was found sufficiently weak but necessary