Although many remarkable results for pion-nucleon interaction have already been reported, no satisfactory explanation for s-wave interaction has yet been given from pion field theory. This situation may be due to the fact that s-wave interaction is strongly affected by the nucleon structure. To our regret, we have not a reliable theory by which the phenomena in the neighborhood of a nucleon core may be explained. The purpose of this paper is to examine how the current pion field theory should

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... modified in such a range as 1/ M and to discuss the assumption which has been introduced in the previous paper. l ) In order to study these problems we think it appropriate to take into consideration the s-wave pion-nucleon scattering. When the real parts of the forward scattering amplitudes for ?r+ -p and ?r--P scattering are denoted by D+ (lU) and D_(w) respectively, the expressions for them can be written down by using the dispersion relation 2 ). In these equations, k is the wave number of pion and lu its total energy, p. and M are the masses of pion and nucleon respectively, andf is equal to (p.g/2M), where g is the renormalized pseudoscalar coupling constant. FI (OJ) and F2(W) stand for the contributions from the bound state and ought to represent the second order perturbation results with renormalized coupling constant. First of all we concentrate our attention on FI (p.) and F2 (p.) in the case of pion momentum k=O. From the expressions of D(2) ((0) in (2) and D(l) (lU) in (1), it may be said that the effects due to the internal structure of nucleon are almost cancelled out in the former, while these effects play an important * With regard to the expressions for GI (w) and G2 (w), see reference 1).