EXCLUSIVE QUASI-FREE PION-PHOTOPRODUCTION ON COMPLEX NUCLEI IN THE DELTA REGION

We present an analysis of the reaction A(gamma, piN)B in the full dist orted wave impulse approximation carried out in momentum space. The bo und nucleon is in a single particle orbital while the outgoing pion an d nucleon are described by appropriate optical potential wave function s. The pion photoproduction operator of Blomqvist and Laget is used. T his reaction allows for more direct studies of DELTA properties in the nuclear medium than the reaction A(gamma, pi)B since the final nucleo n is no longer bound and the sensitivity to the nuclear structure of t he target is thereby largely reduced. Kinematically, the reaction prov ides a great deal of flexibility because the target can take up a wide range of momentum transfer and little energy. Our calculations agree roughly with data from Tomsk but overestimate data from Bates. Nonloca l effects tend to enhance the local cross sections and in some cases a re significant. For future experiments we propose kinematics that grea tly reduce uncertainties from the optical potentials and expose inform ation from the production vertex. We, find that photon asymmetry conta ins such information in the cleanest way and it should be pursued. We suggest forward pion angles where discrepancies between data and theor y exist should be studied more carefully by experiments.