In this review we first outline the basics of transport theory and its recent generalization to offshell transport. We then present in some detail the main ingredients of any transport method using in particular the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) implementation of this theory as an example. We discuss the potentials used, the ground state initialization and the collision term, including the in-medium modifications of the latter. The central part of this review covers applications of GiBUU to a wide class of reactions, starting from pion-induced reactions over proton and antiproton reactions on nuclei to heavy-ion collisions (up to about 30 AGeV). A major part concerns also the description of photon-, electron-and neutrino-induced reactions (in the energy range from a few 100 MeV to a few 100 GeV). For this wide class of reactions GiBUU gives an excellent description with the same physics input and the same code being used. We argue that GiBUU is an indispensable tool for any investigation of nuclear reactions in which final-state interactions play a role. Studies of pion-nucleus interactions, nuclear fragmentation, heavy-ion reactions, hypernucleus formation, hadronization, color transparency, electronnucleus collisions and neutrino-nucleus interactions are all possible applications of GiBUU and are discussed in this article.

We present a model for electron-and neutrino-scattering off nucleons and nuclei focussing on the quasielastic and resonance region. The lepton-nucleon reaction is described within a relativistic formalism that includes, besides quasielastic scattering, the excitation of 13 N * and ∆ resonances and a non-resonant single-pion background. Recent electron-scattering data is used for the state-ofthe-art parametrizations of the vector form factors; the axial couplings are determined via PCAC and, in the case of the ∆ resonance, the axial form factor is refitted using neutrino-scattering data. Scattering off nuclei is treated within the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) framework that takes into account various nuclear effects: the local density approximation for the nuclear ground state; mean-field potentials and in-medium spectral functions. Results for inclusive scattering off Oxygen are presented and, in the case of electron-induced reactions, compared to experimental data and other models.

We have developed a model to describe the interactions of neutrinos with nucleons and nuclei, focusing on the region of the quasielastic and ∆(1232) peaks. We describe neutrino-nucleon collisions with a fully relativistic formalism which incorporates state-of-the-art parametrizations of the form factors for both the nucleon and the N − ∆ transition. The model has then been extended to finite nuclei, taking into account nuclear effects such as Fermi motion, Pauli blocking (both within the local density approximation), nuclear binding and final-state interactions. The in-medium modification of the ∆ resonance due to Pauli blocking and collisional broadening have also been included. Finalstate interactions are implemented by means of the Boltzmann-Uehling-Uhlenbeck (BUU) coupledchannel transport model. Results for charged current inclusive cross sections and exclusive channels as pion production and nucleon knockout are presented and discussed.

We investigate neutrino induced one pion production on nucleons. The elementary neutrinonucleon cross section is calculated as the sum of the leading Delta pole diagram and several background diagrams obtained within the nonlinear sigma model. This approach does not introduce any new adjustable parameters, which allows unambiguous predictions for the observables. Considering electroproduction experiments as benchmark, the model is shown to be applicable up to pion-nucleon invariant mass W < 1.4 GeV and provides a good accuracy. With respect to the total one pion cross section, the model predicts the background at the level of 10% for the pπ + , 30% for pπ 0 , and 50% for nπ + final states. The results are compared with experimental data for various differential cross sections. Distributions with respect to muon-nucleon and muon-pion invariant masses are presented for the first time. The model describes the data quite well, with the discrepancies being of the same order as those between different data sets.

We apply the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) model to questions relevant to current and future long-baseline neutrino experiments, and we address in particular the relevance of charged-current reactions for neutrino-disappearance experiments. A correct identification of charged-current quasielastic (CCQE) eventswhich is the signal channel in oscillation experiments-is relevant for neutrino energy reconstruction and thus for the oscillation result. We show that about 20% of the quasielastic cross section is misidentified in present-day experiments and has to be corrected for by means of event generators. Furthermore, we show that a significant part of 1π + (> 40%) events is misidentified as CCQE events, mainly caused by pion absorption in the nucleus. We also discuss the dependence of both of these numbers on experimental detection thresholds. We further investigate the influence of final-state interactions on the neutrino energy reconstruction.