Deuteron photodisintegration. I. Theory and results at low energies

Abstract

We extend the “elementary-particle treatment” of deuteron electrodisintegration at small excitation energies, as recently developed by Hwang, Henley, and Miller, by incorporating more ( np)-scattering states so that deuteron disintegration by low-energy photons (e.g., ≤150 MeV) can also be investigated. As compared to the well-known formalism obtained by Partovi, the present theory has the following distinct features: The nucleon-only impulse approximation (NOIA), as modified to incorporate gauge invariance (GI), is assumed to be valid only in the Breit frame, in which the initial and final nuclear systems are treated symmetrically. The matrix element of the electromagnetic current is thus determined in the Breit frame and then transformed into the CM frame (i.e., the rest frame for the final n + p, or initial γ + D, system). In addition, the difference between the resultant NOIA GI and the NOIA is determined explicitly in every channel. Numerical results are obtained for the Reid soft-core potential with extensions required for J > 2 scattering states. Our major result is that there is no substantial discrepancy between the θ p = 0° data of Hughes et al. and the prediction of this formalism. General features of this formalism, including angular distributions at low energies, are discussed in quantitative terms. Other important results at these energies include: (1) the 3F J(np) -scattering states are found to be important for E γ ≥ 20 MeV, especially at forward and backward angles (i.e., θ p ∼ 0° or 180°); (2) the meson-exchange currents arising from intermediate isobar |Δ(1232)| propagation, with or without energy transfer effects, are not yet of any numerical significance; and (3) the results exhibit sensitivity to details of final-state interactions.