New Methods in Direct Interaction Theory

Abstract

Methods developed in modern field theory are applied to deuteron stripping. The contribution associated with the direct interaction mechanism is written as the product of two parts, one representing deuteron disassociation in the field of the target and the other nucleon capture by the target. The capture amplitude is written as a dispersion relation and evaluated in terms of the bound-state wave function and the optical model phase shifts for nucleon-nucleus scattering in the capturing channel. The disassociation is also expressed as a dispersion relation and evaluated in terms of the same nucleon-nucleus scattering and also deuteron-target scattering on the energy shell. It is shown that the formalism allows for the distortion of the capture vertex characterized normally by an unusually large nuclear radius, and also explains the persistence of an angular distribution typical of the cutoff Born approximation in spite of a fluctuating yield for the reaction.