Determination of the $πNN$ form factor from the threshold pion production of $pp$ scattering

Abstract

It is shown that the threshold productions of $π^0 pp$, $π^+ np$ and $π^+ d$ from $pp$ collisions can be consistently described by a model consisting of a pion s-wave rescattering and $N\bar N$ pair-terms of heavy-meson exchanges. The large difference between $σ^{tot} (pp\rightarrowπ^+ d)$ and $σ^{tot} (pp\rightarrowπ^+ np)$ is understood from the orthogonality of the deuteron and the $np$ scattering wave functions. In a calculation using the Paris potential to account for the initial and final $NN$ interactions, it is found that the data can be best reproduced by using a soft $πNN$ form factor with $Λ_π =650 $ MeV for a monopole form. This is consistent with an earlier study of pion production in the $Δ$ excitation region.