Generalization of the peripheral model with inclusion of rescattering for (. cap alpha. , 2. cap alpha. ) reactions

A peripheral model is proposed for calculations of the quasielastic knockout (..cap alpha.., 2..cap alpha..) in which one includes explicitly the contributions to the reaction amplitude from the pole and triangle Feynman diagrams corresponding to rescattering in the final state. The peripheral character of the (..cap alpha.., 2..cap alpha..) reaction in the vicinity of the quasielastic peak is taken into account phenomenologically by suppressing the contribution to the reaction amplitude from the internal region of the target nucleus. The model proposed is applied to the description of the reaction /sup 6/Li(..cap alpha.., 2..cap alpha..)/sup 2/H at ..cap alpha..-particle energies E/sub 0/ = 40--80 MeV. The differential cross sections calculated are in good agreement with the measured values. The importance of the inclusion of rescattering effects even in the peripheral region of the reaction amplitude is shown. The nuclear vertex constants for /sup 6/Li ..-->.. ..cap alpha..+d are extracted from the analysis of experimental data.