Theoretical calculation of the forward cross section for deuteron photodisintegration up to 120 MeV

The forward differential cross section for γd → pn in the c.m. frame is calculated for laboratory photon energies up to 120 MeV, using the Paris potential and including relativistic corrections to the impulse approximation and the effect of one-pion exchange, with and without Δ(1231) intermediate states. We give a full treatment of one-pion exchange effects and show that the correction due to them is small (except at energies below 20 MeV) and that it can be accurately calculated. We give a consistent relativistic treatment of the two-nucleon system and correct errors in the well-known work of Partovi which arise from his nonrelativistic treatment. It is shown that the calculated cross section is very sensitive to charge-dependent effects in the one-pion exchange part of the nucleon-nucleon potential and that it is possible to obtain reasonable agreement with the present experimental data when the potential used to calculate the T = 1 np wave functions has a one-pion exchange part which takes account of the masses and coupling constants of both neutral and charged pions.