  Background. Neutrino-induced pion production can give important informationon
the axial coupling to nucleon resonances. Furthermore, pion production
represents a major background to quasielastic-like events. Single pion
production data from the MiniBooNE in charged current neutrino scattering in
mineral oil appeared higher than expected within conventional theoretical
approaches.
  Purpose. We aim to investigate which model parameters affect the calculated
cross section and how they do this.
  Method. The Giessen Boltzmann--Uehling--Uhlenbeck (GiBUU) model is used for
an investigation of neutrino-nucleus reactions.
  Results. Presented are integrated and differential cross sections for 1\pi^+
and 1\pi^0 production before and after final state interactions in comparison
with the MiniBooNE data.
  Conclusions. For the MiniBooNE flux all processes (QE, 1\pi-background,
\Delta, higher resonance production, DIS) contribute to the observed final
state with one pion of a given charge. The uncertainty in elementary pion
production cross sections leads to a corresponding uncertainty in the nuclear
cross sections. Final state interactions change the shape of the muon-related
observables only slightly, but they significantly change the shape of pion
distributions.
