The quasi-elastic knockout of alpha particles from 16O and 28Si by 0.65 and 0.85 GeV alpha particles

Abstract

Measurements of the (α, 2α) reaction in the GeV region on 16O and 28Si are described. The results are compared with a calculation employing the plane wave impulse approximation (PWIA) and with a calculation employing the distorted wave impulse approximation (DWIA). The PWIA calculation reproduces the shape of the angular distribution of the observed quasi-elastic events. The main effect of the distortion introduced in the DWIA calculation is to attenuate the quasi-elastic cross section by a factor of five. As a consequence, the (α, 2α) reaction in the GeV region is expected to be more useful to measure the spectroscopic factor N eff than in the region below 100 MeV since the attenuation is considerably larger (≈ 10 3) in the latter case.