Abstract: Since there is no first principle solution of the many-body problem in quantum chromodynamics, effective theoretical models are necessary to describe the full dynamical evolution of heavy-ion reactions. Hadronic transport approaches offer the possibility to describe the evolution of low energy collisions or the late dilute stages of high energy collisions. In this talk, a new hadronic transport approach (SMASH) is presented. The model is described in detail and validated by comparing the elementary cross section to data.
Furthermore, results for heavy-ion collisions are shown and compared to FOPI and HADES data. The last part focuses on the production of dileptons within this transport approach. The dilepton spectrum also allows access to the electromagnetic transition form factors, which are studied under the hypothesis of vector-meson dominance in a transport picture. The obtained results are compatible with NA60 data. The low-mass dilepton spectrum for proton-proton collisions at 3.5 GeV was measured by HADES. The current status of the comparison with this data sample is given.