Quenching of Cross Sections in Nucleon Transfer Reactions

Cross sections for proton knockout observed in (e,e' p) reactions are apparently quenched by a factor of similar to 0.5, an effect attributed to short-range correlations between nucleons. Here we demonstrate that such quenching is not restricted to proton knockout, but a more general phenomenon associated with any nucleon transfer. Measurements of absolute cross sections on a number of targets between O-16 and Pb-208 were analyzed in a consistent way, with the cross sections reduced to spectroscopic factors through the distorted-wave Born approximation with global optical potentials. Across the 124 cases analyzed here, induced by various proton- and neutron-transfer reactions and with angular momentum transfer l = 0-7, the results are consistent with a quenching factor of 0.55. This is an apparently uniform quenching of single-particle motion in the nuclear medium. The effect is seen not only in (d, p) reactions but also in reactions with A = 3 and 4 projectiles, when realistic wave functions are used for the projectiles.