Determination of the $\pi NN$ form factor from the threshold pion production of $pp$ scattering

Abstract

It is shown that the threshold productions of ${\pi }^{0}pp$, ${\pi }^{+}np$ and ${\pi }^{+}d$ 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 ${\sigma }^{tot}(pp\to {\pi }^{+}d)$ and ${\sigma }^{tot}(pp\to {\pi }^{+}np)$ 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 $\pi NN$ form factor with ${\Lambda }_{\pi }=650$ MeV for a monopole form. This is consistent with an earlier study of pion production in the $\Delta$ excitation region.

Comments: 8 pages