Event-by-event pre-equilibrium evolution in hadron collisions

Extracting the QGP medium properties, like shear or bulk viscosities, is the primary goal of heavy-ion research. However choice of initial conditions for the hydrodynamical evolution of the plasma is the main source of model uncertainties. Therefore the first principle modelling of initial gauge fields, or multi-parameter model-to-data fits have been very important for the progress of the field. However, until recently none of the approaches included the pre-equilibrium physics, which would naturally lead to hydrodynamical expansion of QGP.

In a series of works, we have constructed a linearized response framework based on kinetic theory simulations, which propagates initial non-equilibrium energy-momentum tensor to the time, when the hydrodynamic constitutive equations are satisfied. Our publicly available package KøMPøST is a practical tool to do event-by-event simulations of heavy-ion collisions with realistic pre-equilibrium dynamics.