The Hadron-String Dynamics (HSD) transport approach is a covariant microscopic transport model developed to simulate: relativistic heavy-ion collisions, proton-nucleus reactions, pion-nucleus reactions in the energy range from SIS to RHIC. The Parton-Hadron-String Dynamics transport approach (PHSD) is the extension of HSD for higher energies including the partonic phase. In the low energy sector, PHSD is equivalent to HSD.
The HSD transport approach provides the numerical testparticle solution of a coupled set of relativistic transport equations for particles with in-medium selfenergies. It is based on quark, diquark, string and hadronic degrees of freedom. High energy inelastic hadron-hadron collisions in HSD are described by the FRITIOF string model (including PYTHIA) whereas low energy hadron-hadron collisions are modelled based on experimental cross sections. The transport approach is matched to reproduce the nucleon-nucleon, meson-nucleon and meson-meson cross section data in a wide kinematic range. HSD takes into account the formation and multiple rescattering of leading pre-hadrons and hadrons.
The major aim of HSD is —within a single transport model— to gain an understanding about the nuclear dynamics, the creation of dense and hot hadronic matter and the modification of hadron properties in a medium.