The applicability of hydrodynamics in heavy ion collisions at  = 2.4–7.7 GeV

Gabriele Inghirami; Hannah Elfner

doi:10.1140/epjc/s10052-022-10718-x

2024 Impact factor 4.8

Particles and Fields

Open Access

Eur. Phys. J. C (2022) 82: 796
https://doi.org/10.1140/epjc/s10052-022-10718-x

Regular Article - Theoretical Physics

The applicability of hydrodynamics in heavy ion collisions at $\sqrt{s_{NN}}$ $\sqrt{s_\mathrm{NN}}$ = 2.4–7.7 GeV

Gabriele Inghirami¹^a and Hannah Elfner¹^,2^,3^,4

¹ GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstr. 1, 64291, Darmstadt, Germany
² Institut für Theoretische Physik, Goethe Universität Frankfurt, Max-von-Laue-Straße 1, 60438, Frankfurt am Main, Germany
³ Frankfurt Institute for Advanced Studies, Ruth-Moufang-Straße 1, 60438, Frankfurt am Main, Germany
⁴ Helmholtz Research Academy Hesse for FAIR (HFHF), GSI Helmholtz Center, Campus Frankfurt, Max-von-Laue-Straße 12, 60438, Frankfurt am Main, Germany

^a g.inghirami@gsi.de

Received: 25 January 2022
Accepted: 17 August 2022
Published online: 6 September 2022

Abstract

To assess the degree of equilibration of the matter created in heavy-ion reactions at low to intermediate beam energies, a hadronic transport approach (SMASH) is employed. By using a coarse-graining method, we compute the energy momentum tensor of the system at fixed time steps and evaluate the degree of isotropy of the diagonal terms and the relative magnitude of the off-diagonal terms. This study focuses mostly on Au+Au collisions in the energy range ${\sqrt{s}}_{NN}$ ${\sqrt{s}_\mathrm{NN}}$ = 2.4–7.7 GeV, but central collisions of lighter ions like C+C, Ar+KCl and Ag+Ag are considered as well. We find that the conditions concerning local equilibration for a hydrodynamic description are reasonably satisfied in a large portion of the system for a significant amount of time (several fm/c) when considering the average evolution of many events, yet they are rarely fulfilled on an event by event basis. This is relevant for the application of hybrid approaches at low beam energies as they are or will be reached by the HADES experiment at GSI, the future CBM experiment at FAIR as well as the beam energy scan program at RHIC.

© The Author(s) 2022

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