Considering that, in pp scattering, the pp → n Δ++ transition occurs mainly from the elastic channel, a t-matrix for this process was constructed by us earlier. This t-matrix describes the measured cross-sections on the p (p, n) Δ++ process very well from threshold to a few GeV. The transition potential in it is described by the one pion-exchange potential and the elastic scattering wave function through the "measured" elastic scattering amplitude. In this paper, we have parametrized this t-matrix so that it can be used for describing the (p, Δ++) reaction in nuclei. The parametrized t-matrix has been found to have a structure similar to one pion-exchange potential except that it has a softer form factor (Λ ≈ 650–800 MeV/c ) and it has a Migdal term (g′ ≈ 0.65) in the central term. The imaginary part of the t-matrix is weak. In the single scattering approximation this t-matrix describes the measured cross-sections on p(3 He , t) Δ++ and 6 Li (p, Δ++)6 He reactions very well. It is also found that with this t-matrix, the "projectile excitation" contribution to the reaction is small.
The one-pion-exchange potential in the three-body model of nucleon-nucleon scattering