Photoproduction of negative pions in deuterium

Deuterium provides the most suitable target for studying the basic process of negative pion photo-production at a free neutron. For photon energies well above threshold the spectator model has been used to relate photoproduction in deuterium to photoproduction at a free neutron. Until recently no experimental test of the spectator model that clearly supported its validity for negative pion photoproduction in deuterium had been reported. The spectator model has been investigated using the 307 MeV bremsstrahlung beam of the Glasgow electron synchrotron. The simultaneous detection of pions and protons produced in a thin liquid deuterium target was accomplished using scintillation counter telescopes. The pions were detected at 90 +/- 3.7 degrees in the energy range 46.3 to 60.4 MeV. The angular distribution of recoil protons, and the energy spectrum of recoil protons detected at 30 +/- 3.5 degrees were measured. The measured angular distribution was well described by the angular distribution calculated in the spectator model. The measured energy spectrum has a broad maximum at 42 MeV. The shape of the spectrum although is well described by the spectator model calculation, the measured spectrum appears to be shifted towards higher energy by 3 to 4 MeV. It may be concluded that the spectator model provides a reasonable description of negative pion photoproduction in deuterium for photon energies about 230 MeV. The differential cross section for negative pion photoproduction in deuterium at 90 +/- 3.7 degrees and 53 +/- 7 MeV is 15.8 +/- 1.9 x 10-30 cm2/steradian MeV