Different theoretical models for two- and three-body electromagnetic currents are constructed using meson-exchange mechanisms and minimal substitution in the momentum dependence of two- and three-nucleon interactions. We review the use of effective field theory (EFT) to compute electromagnetic reactions in three-nucleon systems at very low energies. We first explain how EFT theory can be extended to incorporate the photon into the three-nucleon systems when also a three-nucleon force is acting. We also explain the predictions of the resulting EFT for neutron–deuteron radiative capture process at very low energies. In this work, a number of low-energy photonuclear observables, including neutron–deuteron radiative capture reactions and triton photodisintegration, are calculated in order to make a comparative study of the pion-less EFT results with the models based on the realistic Argonne v18(AV18) two-nucleon and Urbana IX or Tucson–Melbourne three-nucleon interactions. The calculated cross-section of neutron–deuteron radiative capture and photon polarization parameter of 3 H are in satisfactory agreement with the available experimental data.
