EXCLUSIVE PION-PRODUCTION IN PROTON-NUCLEUS COLLISIONS AND THE RELATIVISTIC 2 NUCLEON DYNAMICS

The exclusive pion production in a proton-nucleus collision, leading t o two-body final states, is examined in a fully covariant two-nucleon model. We focus on the amplitudes which are dominated by the Delta(123 2) resonance. Retaining the full covariant forms of the pi NN and pi N Delta vertices and employing a relativistic propagator for the delta isobar, expressions for various reaction amplitudes are derived. The b ound state nucleon wave functions are obtained by solving the Dirac eq uation with appropriate scalar and vector potentials whereas the conti nuum wave functions are approximated by plane waves. The sensitivity o f the calculated cross sections to the in-medium self-energy of the in termediate pion is investigated. It is found that the relative magnitu des of the so called target-emission and projectile-emission amplitude s depend strongly on the pion self-energy. A comparison with the avail able data for the C-12 and O-16 targets at the incident proton energy of 800 MeV supports our conclusions.