Unitary meson-exchange πNN models: NN and πd elastic scattering

Within a unitary πNN theory a set of coupled integral equations defined in the NN⊕NΔ ⊕πNN subspace has been derived for examining the extent to which the NN and πd elastic scattering data can be both described by a class of meson-exchange πNN models. The considered models are constructued by using a previously developed subtraction procedure to extend the Paris, Bonn, Argonne-V14, and Reid NN potentials to include the coupling to the πNN production channel. The pion production through the Δ excitation is described by a πN⇆Δ vertex and a $V_{\mathrm{NN}\mathit{\leftrightarrows }\mathrm{N}\mathit{\Delta }}$ transition potential, while the production through nonresonant πN interactions is described by a transition operator $F_{\pi \mathrm{NN}\mathit{\leftrightarrows }\mathrm{NN}}$. It is found that none of the constructed models can accurately reproduce all NN and πd elastic scattering data, in particularly the data of polarization observables. Our results indicate that either the conventional phenomenological parametrizations of baryon-baryon interaction at short distances are not valid in the intermediate energy region, or some genuine quark dynamics has already been revealed in the πNN data.