Particlization in hybrid models

Abstract

Abstract. In hybrid models, which combine hydrodynamical and transport approaches to describe different stages of heavy-ion collisions, conversion of fluid to individual particles, particlization, is a non-trivial technical problem. We describe in detail how to find the particlization hypersurface in a 3+1 dimensional model, and how to sample the particle distributions evaluated using the Cooper-Frye procedure to create an ensemble of particles as an initial state for the transport stage. We also discuss the role and magnitude of the negative contributions in the Cooper-Frye procedure.

Initial state fluctuations and final state correlations in relativistic heavy-ion collisions

“…For the sampling procedure itself, there are many different algorithms developed by different groups [75] (and references therein). It would be desirable to standardize the procedure, clarify the crucial steps and create an efficient routine that is available as open source code.…”

Hadron rapidity spectra within a hybrid model

“…To define an integration hypersurface on which the "instantaneous" transition from a liquid fluid to freely expanding particles occurs, we use the CORNELIUS algorithm [13], whose realization is available freely. We consider different freeze-out scenarios: 1) isochronous, when the calculation is completed at the given time moment; 2) isothermal (iso-T ), when the cell is frozen if its temperature is less or equal the freeze-out temperature T ≤ T frz , and 3) isoenergetic (iso-ε), which is entirely analogous to the isothermal one where the energy density plays the role of temperature.…”

MUSIC with the UrQMD Afterburner

“…(See also Ref. [27] for an exact freeze-out-surface finding algorithm.) One missing ingredient is the viscous correction of the thermal distribution when it is sampled for the subsequent UrQMD run.…”