Dielectron production in proton-proton and proton-deuteron collisions at 1-5 GeV

Estimates of elementary cross sections for dielectron production in pN-and pd-reactions are presented. We use throughout the vector dominance model for all hadron-hadron-photon vertices. Dynamical suppression mechanisms (e.g., mass dependent Δ production rate, and the correct energy dependence of the two-body T matrix) bring the elementary rate near to experimental data and previous estimates which do not use vector meson dominance. The Δ, η Dalitz decays and Bremsstrahlung appear as dominant sources of di electrons. Bremsstrahlung is dealt within an improved soft photon approximation which also applies for the pp-collisions. At higher energies the Bremsstrahlung contribution is only a subclass of direct vector meson decays. Relying on a realistic deuteron wave function we also estimate the energy dependence of the ratio of dielectron yields in pd- to pp-reactions and find good agreement with new experimental results. 40 refs., 7 figs