Electromagnetic Transitions for the Photodisintegration of the Deuteron

Abstract

Over-all electromagnetic transitions for the photodisintegration of the deuteron are examined in the energy range 162 to 833 MeV. The virtual meson exchange interaction is not considered. The electromagnetic interactions are treated without any series expansion. Therefore, all multipole transitions and their retardations are completely taken into account in the calculations.The pion-theoretical deuteron wave function and plane waves are used for the initial and final states, neglecting the effects of the hard core in the nucleon-nucleon potential. It is then shown that the angular dependence of those terms which are simply isotropic in the electric dipole approximation is given approximately by the isotropic part in the electric dipole transition, plus a cosine curve due to the overlap effects of the higher multipole transitions, as well as overlap effects due to all retardations. The terms which reduce to the anisotropic terms in the electric dipole approximation give angular distributions which are shifted forward from sin% but which tend to flatten out with increasing energy. The separate retardation effects due to the dipole and other multipole terms cannot be distinguished in the present calculation.For some reason the total cross sections seem to fit the experimental data fairly well at energies higher than 400 MeV when only the electric transitions are taken into account. However, the total cross sections including magnetic transitions are about four times the experimental data at 800 MeV. The contribution of the magnetic transitions to the cross sections does not decrease as much with energy as does the contribution due to the electric transitions and remains relatively large at high energy. The effect of disregarding the hard core is large for the spin magnetic transitions.

Threshold photoproduction of neutral pions off protons in nuclearmodel with explicit mesons

“…Since the wavelength of a photon with the energy hω > ∼ mπ is on the order of the size of the dressed proton we have to calculate the cross-section without the use of the usual multipole expansion of the electromagnetic operator (cf. [12]).…”