COMPARISON OF THE QUASI-ELASTIC (E, E'P) AND THE (GAMMA, P) REACTIONS

Recent data obtained with the quasielastic (e, e'p) reaction, and the (gamma, p) reaction at photon energies of about 60 MeV, on C-12, O-16, Al-27, Ca-40, and V-51 are examined. Comparisons are made using distorted-wave impulse-approximation calculations. The (e, e/p) data are used to determine the values of spectroscopic factors and root-mean-square radii of the overlap wave function for each transition considered. These parameters constrain the direct-knockout (DKO) calculations for the (gamma, p) reactions which have been performed within the same framework. While the calculations give a very good description of the (e, e'p) data, a discrepancy of typically a factor of six is observed between the DKO calculations and the (gamma, p) data. The discrepancy is largely removed when meson exchange current contributions in the (gamma, p) reaction are estimated on the basis of the Siegert theorem.