Research
The microscopic theory of complex many-body systems and in particular of high-energy nucleus-nucleus collisions is based on relativistic transport equations of the various degrees-of-freedom, i.e. hadrons at low energy density or quarks and gluons above the critical energy density for deconfinement. We explore numerically on what time-scales these systems achieve kinetic and chemical equilibrium and calculate the macroscopic transport properties like shear and bulk viscosity in equilibrium. Furthermore, the collective response of these systems to initial fluctuations of energy density in coordinate space is explored and for the case of heavy-ion collisions compared to experimental data for charged hadron angular distributions in the azimuthal angle as well as for a set of fluctuation observables.
A further focus lies on the electromagnetic radiation from these strongly interacting systems, i.e. either the emission of photons or the radiation of dilepton pairs. Closely linked to these questions is the dynamics of heavy (charm and bottom) quarks which decay to leptons by the weak interactions and contribute as 'background' to the dilepton spectra measured experimentally. These 'hard' probes are complemented by the dynamics of quarks with high transverse momenta which loose energy during the propagation through the partonic plasma and provide sensitive information on the parton interaction rates.
All these observables are evaluated in close contact with experimental collaborations at FAIR/GSI (Darmstadt), CERN (Geneva) as well as RHIC (Brookhaven).
PHSD simulation of Au+Au collision at center of mass energy 200 GeV