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Pion-Production in Heavy-Ion Collisions at SIS energies

We investigate the production of pions in heavy-ion collisions in the energy range of $1$ - $2$ GeV/A. The dynamics of the nucleus-nucleus collisions is described by a set of coupled transport equations of the Boltzmann-Uehling-Uhlenbeck type for baryons and mesons. Besides the $N(938)$ and the $Δ(1232)$ we also take into account nucleon resonances up to masses of $1.9 GeV/c^2$ as well as $π$-, $η$- and $ρ$-mesons. We study in detail the influence of the higher baryonic resonances and the $2π$-production channels ($NN\to NN ππ$) on the pion spectra in comparison to $π^-$ data from $Ar + KCl$ collisions at $1.8$ GeV/A and $π^0$-data for $Au+Au$ at 1.0 GeV/A. We, furthermore, present a detailed comparison of differential pion angular distributions with the BEVALAC data for Ar + KCl at 1.8 GeV/A. The general agreement obtained indicates that the overall reactions dynamics is well described by our novel transport approach.