Nuclear pion photoproduction in the Delta resonance region

A measurement of the /sup 12/C( gamma , pi /sup +/n)/sup 11/B reaction in quasifree pi -production kinematic regimes has been performed using tagged photons in conjunction with large solid angle pi and n detectors. The aim of the experiment was to investigate predicted modifications to the Delta excitation of nucleons and their subsequent propagation and decay, brought about by the nuclear medium. Differential cross sections are presented for photon energies spanning the Delta (1232) excitation region. The measurements are consistent with distorted wave impulse approximation calculations in which the amplitude for proton Delta excitation, followed by Delta propagation and decay to pi /sup +/+n, is reduced compared to that for a free p. However, because of uncertainties in the magnitudes of the final state interactions, it is concluded that improved calculations are required to obtain a quantitative estimate of Delta - medium effects