Dilepton production in nucleon-nucleon interactions

Starting from a realistic one-boson-exchange model fitted to the amplitudes of elastic nucleon-nucleon scattering and the process NN→NΔ we perform a fully relativistic and gauge-invariant calculation for the dilepton production in nucleon-nucleon collisions, including the important effect of propagating the Δ-resonance. We compare the results of our calculations with the latest experimental data on dilepton production. We also show how to implement various electromagnetic form factors for the hadrons in our calculations without losing gauge invariance and discuss their influence on dilepton spectra. ((orig.))