pp annihilation into π+π−π0 in a hadron-exchange model

Proton-antiproton annihilation into three pions is studied in a hadron-exchange model. An uncorrelated three-pion channel is added to the two-meson channels considered in previous calculations. Initial-state interactions are taken into account in a distorted-wave Born approximation, using the most complete version of the Jülich NN model. The uncorrelated three-pion channel adds a 10% contribution to the pp → π+π−π0 total cross section. The relative branching ratios for annihilation into three uncorrelated pions from states of equal orbital angular momentum, but different total angular momentum and spin, are also calculated. They compare semi-quantitatively with the corresponding quantities calculated from the phase-space components of phenomenological amplitudes fitted to experimental data for stopped antiprotons. It is concluded that hadron exchange provides a viable model for annihilation into three non-resonant pions.