Effects of the QCD phase transition on hadronic observables in relativistic hydrodynamic simulations of heavy-ion reactions in the FAIR/NICA energy regime

Abstract

We investigate hadronic particle spectra and flow characteristics of heavy-ion reactions in the FAIR/NICA energy range of 1 AGeV ≤ E lab ≤ 10 AGeV within a relativistic ideal hydrodynamic one-fluid approach. The particlization is realized by sampling the Cooper-Frye distribution for a grand canonical hadron gas on a hypersurface of constant energy density. Results of the hydrodynamic calculations for different underlying equations of state are presented and compared with experimental data and microscopic transport simulations. The sensitivity of the approach to physical model inputs concerning the initial state and the particlization is studied.

Future physics perspectives on the equation of state from heavy ion collisions to neutron stars

“…Such a framework does not yet exist for data at low beam energies due to the issues outlined above and laid out in figure 4. While initial attempts have been made for comparing ideal hydrodynamics [244] to experimental data at low beam energies, one must incorporate in this case transport coefficients, as there are many indications that the influence of out-of-equilibrium effects only grows with lower beam energies. Thus, we emphasize that the problem is not reference [243] but rather the misuse of their results as a de facto experimental heavy ion constraint that must be used to eliminate certain physical scenarios concerning the high density regime of the EoS in neutron stars.…”

“…Instead, what has usually been done is to either compare hadronic models (transport) to experimental data and attempt to extract the EoS from such models (this was done in [243,245]) or to compare ideal hydrodynamics to data with different EoS assumptions, as was done in [244]. At the moment, neither are a perfect fit to experimental data and fail to capture a number of experimental observables.…”

Future Physics Perspectives on the Equation of State from Heavy Ion Collisions to Neutron Stars

“…4. While initial attempts have been made for comparing ideal hydrodynamics [241] to experimental data at low beam energies, one must incorporate in this case transport coefficients, as there are many indications that the influence of out-of-equilibrium effects only grows with lower beam energies. Thus, we emphasize that the problem is not Ref.…”

“…Instead, what has usually been done is to either compare hadronic models (transport) to experimental data and attempt to extract the EoS from such models (this was done in [240,242]) or to compare ideal hydrodynamics to data with different EoS assumptions, as was done in [241]. At the moment, neither are a perfect fit to experimental data and fail to capture a number of experimental observables.…”