A microscopic model for the NN¯→ππ process is presented in the meson exchange framework, which in the pseudophysical region agrees with available quasiempirical information. The scalar (σ) and vector (ρ) piece of correlated two-pion exchange in the pion-nucleon interaction is then derived via dispersion integrals over the unitarity cut. Inherent ambiguities in the method and implications for the description of pion-nucleon scattering data are discussed.

• Received 6 September 1994

DOI:https://doi.org/10.1103/PhysRevC.51.1374