Differential cross section and analysing power of the quasi-free pn -> {pp}_s pi- reaction at 353 MeV

Abstract

In order to establish links between p-wave pion production in nucleon-nucleon collisions and low energy three-nucleon scattering, an extensive programme of experiments on pion production is currently underway at COSY-ANKE. The final proton pair is measured at very low excitation energy, leading to an S-wave diproton, denoted here as {pp}_s. By using a deuterium target we have obtained data on the differential cross section and analysing power of the quasi-free pol{p}n -> {pp}_s pi^- reaction at 353 MeV. The spectator proton p_sp was either measured directly in silicon tracking telescopes or reconstructed using the momentum of a detected pi^-. Both observables can be described in terms of s-, p-, and d-wave pion production amplitudes. Taken together with the analogous data on the pol{p}p -> {pp}_s pi^0 reaction, full partial wave decompositions of both processes were carried out.