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

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 $\sqrt{s_{\mathrm{NN}}}$ = 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.

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References in corpus (26)

• PYTHIA 6.4 Physics and Manual
• An Introduction to PYTHIA 8.2
• The QCD equation of state with dynamical quarks
• Elliptic and triangular flow in event-by-event (3+1)D viscous hydrodynamics
• Equation of state and QCD transition at finite temperature
• Alternative ansatz to wounded nucleon and binary collision scaling in high-energy nuclear collisions
• Highly-anisotropic and strongly-dissipative hydrodynamics for early stages of relativistic heavy-ion collisions
• Parton transport and hadronization from the dynamical quasiparticle point of view
• GLISSANDO: GLauber Initial-State Simulation AND mOre
• Event-by-event hydrodynamics and elliptic flow from fluctuating initial state
• A kinetic regime of hydrodynamic fluctuations and long time tails for a Bjorken expansion
• Do nuclear collisions create a locally equilibrated quark-gluon plasma?
• Comparison of Heavy-Ion Transport Simulations: Mean-field Dynamics in a Box
• Analytical and numerical Gubser solutions of the second-order hydrodynamics
• Global $\Lambda$ polarization in moderately relativistic nuclear collisions
• Particlization of an interacting hadron resonance gas with global conservation laws for event-by-event fluctuations in heavy-ion collisions
• Hydrodynamics from free-streaming to thermalization and back again
• Anisotropic flow in transport+hydrodynamics hybrid approaches
• How large is the Knudsen number reached in fluid dynamical simulations of ultrarelativistic heavy ion collisions?
• Benchmarking a Non-Equilibrium Approach to Photon Emission in Relativistic Heavy-Ion Collisions
• Hadron resonance gas with van der Waals interactions
• Systematic Investigation of Negative Cooper-Frye Contributions in Heavy Ion Collisions Using Coarse-grained Molecular Dynamics
• Different Realizations of Cooper-Frye Sampling with Conservation Laws
• Particle Production in AgAg Collisions at $E_{\mathrm{Kin}}=1.58A$ GeV within a Hadronic Transport Approach
• Probing dense QCD matter in the laboratory: The CBM experiment at FAIR
• Conservation laws in a novel hybrid approach

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