Dielectron production in proton-proton and proton-deuteron collisions at 1–2 GeV

Estimates of elementary cross sections for dielectron production in pN and pd reactions are presented. Throughout, we use the vector dominance model for all hadron-hadron-photon vertices. The Δ,η Dalitz decays and bremsstrahlung appears as dominant sources of dielectrons. We show that the recently observed strong enhancement from 2 of the ratio of dielectron production from pd to pp collision at low energy E∼1.0–1.3 GeV may be understood by a different threshold behavior of eta production in proton-proton and proton-neutron collisions. Relying on a realistic deuteron wave function we estimate the energy dependence of the ratio and find qualitative agreement with new experimental results.