Photo- and electro-disintegration of the deuteron in the GeV range

The process γ(*)d→pn is investigated up to photon lab.-energies of 1.6 GeV in a relativistic covariant approach based on conventional quantum field theory. Using effective lagrangians for the hadron interactions we have applied consequently the method of Feynman graphs to approximate the dynamics of deuteron photo- and electro-disintegration. It is demonstrated that in the considered energy region the relativistic structure of the dNN-vertex, the usually neglected offshell effects and the contributions of the higher nucleon resonances play a significant role. A central point in our calculations is the treatment of Feynman box diagrams where the exchange of π-, ρ-, ω- and η-meson and all nucleon- and delta-resonances of the data booklet with mass m*<2 GeV and spin ≤5/2 have been included. As usual form factors for the meson-baryon couplings are introduced to take account of the composite structure of hadrons. Our investigations show that the monopol ansatz for their parametrization is only realistic at low photon energies. Subsequently retaining gauge invariance of the amplitudes has to be considered carefully. A detailed comparison of our calculations with the existing experimental differential cross section data and polarization measurements is carried out. It is shown that the recoil nucleon polarization around 600 MeV is not necessarily demanding the existence of multiquark baryonic states. (orig.)