  Background: Charged current pion production gives information on the axial
formfactors of nucleon resonances. It also introduces a noticeable background
to quasi-elastic measurements on nuclear targets. Purpose: Understand pion
production in neutrino interactions with nucleons and the reaction mechanism in
nuclei. Method: The Giessen Boltzmann--Uehling--Uhlenbeck (GiBUU) model is used
for an investigation of neutrino-nucleus reactions. Results: Theoretical
results for integrated and differential cross sections for the MiniBooNE
neutrino flux are compared to the data. Two sets of pion production data on
elementary targets are used to obtain limits for the neutrino-nucleus
reactions. Conclusions: The MiniBooNE pion production data are consistent with
the BNL elementary data if a small flux renormalization is performed while the
ANL input data lead to significantly too low cross sections. A final
determination of in-medium effects requires new data on elementary (p,D)
targets.
