The FLUKA hadron-nucleon interaction models are based on resonance production and decay below a few GeV, and on the Dual Parton model above. Two models are used also in hadron-nucleus interactions. At momenta below 3--5 GeV/c the PEANUT package includes a very detailed Generalised Intra-Nuclear Cascade (GINC) and a preequilibrium stage, while at high energies the Gribov-Glauber multiple collision mechanism is included in a less refined GINC. Both modules are followed by equilibrium processes: evaporation, fission, Fermi break-up, gamma deexcitation. FLUKA can also simulate photonuclear interactions (described by Vector Meson Dominance, Delta Resonance, Quasi-Deuteron and Giant Dipole Resonance), electronuclear interactions, photomuon production and electromagnetic dissociation. A schematic outline is presented below: * Inelastic cross sections for hadron-hadron interactions are represented by parameterised fits based on available experimental data [PDG]. * For hadron-nucleus interactions, a mixture of tabulated data and parameterised fits is used [Bar72, Moh83, She91, Pra98, Pra98a]. * Elastic and charge exchange reactions are described by phase-shift analyses and eikonal approximation. * Inelastic hadron-hadron interactions are simulated by different event generators, depending on energy: - Momentum < 20 TeV and > 5 GeV/c: Dual Parton Model (DPM) [Cap94]. The version used in FLUKA has been derived by A. Ferrari and P.R. Sala [Fer94, Fas95, Fer95, Fer96b] from the original version by J. Ranft and collaborators [Ran83, Ran83a]. A description of modifications and improvements can be found in [Fer96b, Col00] - Momentum from threshold to 5 GeV/c: Resonance production and decay model [Fer96b] (Improved version of the H"anssgen et al. model [Han79, Han80, Han84, Han84a, Han84b, Han86, Han86a]) * Inelastic hadron-nucleus interactions are simulated by different event generators depending on energy and projectile: - Momentum < 20 TeV and > 5 GeV/c: Glauber-Gribov multiple scattering followed by Generalized Intranuclear Cascade (GINC) - Below 5 GeV/c for nucleons, anti-nucleons and pions; below 1.5 GeV kinetic for kaons: Preequilibrium-cascade model PEANUT (Ferrari-Sala) [Fer94, Fas95] - In between PEANUT and DPM for kaons: K. H"anssgen et al. GINC modified to take into account correlations among cascade particles and more refined nuclear effects (Ferrari-Sala). * All three models include evaporation and gamma deexcitation of the residual nucleus [Fer96, Fer96a]. Light residual nuclei are not evaporated but fragmented into a maximum of 6 bodies, according to a Fermi break-up model. * Treatment of antiparticle capture: the basic antinucleon-nucleon process is modeled through the production and decay of two or more intermediate states whose branchings are adjusted to reproduce experimental pion/kaon/resonances multiplicities. In nuclei, all nuclear effects (density, Fermi motion, Pauli-blocking, re-interaction of secondaries...) are treated by the PEANUT model as for all other hadronic interactions. Annihilations occur at shallow depths inside the nucleus. The depth is chosen as a function of the atomic number, the interaction being more and more peripheral as the nuclear mass increases. In case of compounds, the relative annihilation probabilities are calculated following [Pon73] for hydrogenated compounds, and [Dan75] for other compounds.
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