Nuclear pion photoproduction in the Delta resonance region - art. no. 014603

A measurement of the C-12(gamma,pi(+)n)B-11 reaction in quasifree pi-produc tion kinematic regimes has been performed using tagged photons in conjuncti on 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 m edium. Differential cross sections an presented for photon energies spannin g the Delta(1232) excitation region. The measurements are consistent with d istorted wave impulse approximation calculations in which the amplitude for proton Delta excitation, followed by Delta propagation and decay to pi(+)n, is reduced compared to that for a free p. However, because of uncertaint ies in the magnitudes of the final state interactions, it is concluded that improved calculations are required to obtain a quantitative estimate of De lta-medium effects.