Pre-equilibrium Flow Effects and Applicability of Hydrodynamics in High-Energy Collisions

by Clemens Werthmann (University of Wroclaw)

Monday 25 Sept 2023, 17:00 → 18:30 Europe/Zurich

4/2-037 - TH meeting room (CERN)

We simulate the space-time dynamics of high-energy collisions based on a microscopic kinetic description, in order to determine the range of applicability of an effective description of the bulk dynamics in relativistic viscous hydrodynamics. One of the main advantages of the kinetic theory based description over hydrodynamics is that it can also accurately describe pre-equilibrium. We examine several flow related pre-equilibrium effects in analytically treatable limiting cases as well as numerical simulation codes.
We find that hydrodynamics provides a quantitatively accurate description of collective flow when the average inverse Reynolds number Re^−1 is sufficiently small and the early pre-equilibrium stage is properly accounted for. By determining the breakdown of hydrodynamics as a function of system size and energy, we find that it is quantitatively accurate in central lead-lead collisions at LHC energies, but should not be used in typical proton-lead or proton-proton collisions, where the development of collective flow can not accurately be described within hydrodynamics.
 

We are now working on the search for observables that carry direct information on the degree of hydrodynamization of different collision system by performing event-by-event simulations, and I will present some preliminary results.