The VII-th International Conference on the Initial Stages of High-Energy Nuclear Collisions : Initial Stages 2023

Hydrodynamic description of heavy ion collisions using the EKRT model with dynamical decoupling

Not scheduled

20m

Copenhagen

Poster Collective dynamics from small to large systems

Speakers

Henry Hirvonen (University of Jyväskylä)Prof. Kari J. Eskola (University of Jyväskylä (FI)) Harri Niemi (University of Jyväskylä)

Description

In the EKRT model for ultrarelativistic heavy-ion collisions, we compute the initial fluctuating QCD-matter energy densities from NLO pQCD and saturation, and describe the subsequent space-time evolution of the system with dissipative fluid dynamics, event by event [1,2,3]. This model agrees remarkably well with the low-$p_T$ flow observables measured in Pb+Pb and Xe+Xe collisions at the LHC, and Au+Au collisions at RHIC, in the centrality range 0-50 \%. To extend this validity range further, and to perform a simultaneous comparison of the centrality dependence of hadronic multiplicities, $p_T$ spectra and various flow correlators against the latest LHC and RHIC data, we have now improved the fluid-dynamics part of the model significantly [4]. An essential new feature is the dynamical freeze-out that accounts both for a local Knudsen-number based criterion, and for a global criterion set by the overall size of the system. Importantly, our model is based purely on hydrodynamics also in the hadronic phase, so that a continuous parametrization of the temperature dependence of transport coefficients is possible. Adding a non-zero bulk viscosity and taking the chemical freeze-out at $T=155$ MeV, we obtain a good simultaneous description of the average $p_T$ and the proton multiplicity, and at the same time we show that the setup clearly improves the agreement with the $v_n\{2\}$ LHC measurements in peripheral collisions while maintaining the earlier good agreement with other flow correlations. We also show that bulk viscosity together with the dynamical freeze-out clearly improves the quantitative description of the recently measured $p_T,v_n$ correlations.

[1] H. Niemi, K. J. Eskola and R. Paatelainen, Phys. Rev. C 93, no.2, 024907 (2016)
[2] H. Niemi, K. J. Eskola, R. Paatelainen and K. Tuominen, Phys. Rev. C 93, no.1, 014912 (2016)
[3] K. J. Eskola, H. Niemi, R. Paatelainen and K. Tuominen, Phys. Rev. C 97, no.3, 034911 (2018)
[4] H. Hirvonen, K. J. Eskola, H. Niemi, Phys. Rev. C 106, no.4, 044913 (2022)