Relativistic heavy-ion collisions within three-fluid hydrodynamics: Hadronic scenario

Abstract

A 3-fluid hydrodynamic model for simulating relativistic heavy-ion collisions is introduced. Alongside with two baryon-rich fluids, the new model considers time-delayed evolution of a third, baryonfree (i.e. with zero net baryonic charge) fluid of newly produced particles. Its evolution is delayed due to a formation time τ , during which the baryon-free fluid neither thermalizes nor interacts with the baryon-rich fluids. After the formation it starts to interact with the baryon-rich fluids and quickly gets thermalized. Within this model with pure hadronic equation of state, a systematic analysis of various observables at incident energies between few and about 160A GeV has been done as well as comparison with results of transport models. We have succeeded to reasonably reproduce a great body of experimental data in the incident energy range of E lab ≃ (1-160)A GeV. The list includes proton and pion rapidity distributions, proton transverse-mass spectra, rapidity distributions of Λ andΛ hyperons, elliptic flow of protons and pions (with the exception of proton v2 at 40A GeV), multiplicities of pions, positive kaons, φ mesons, hyperons and antihyperons, including multi-strange particles. This agreement is achieved on the expense of substantial enhancement of the interflow friction as compared to that estimated proceeding from hadronic free cross sections. However, we have also found out certain problems. The calculated yield of K − is approximately by a factor of 1.5 higher than that in the experiment. We have also failed to describe directed transverse flow of protons and pion at E lab ≥ 40A GeV. This failure apparently indicates that the used EoS is too hard and thereby leaves room for a phase transition.

Elliptic flow and dissipation in heavy-ion collisions atElab≃(1–160)AGeV

“…Figure 1 illustrates the results of Ref. [28]. Here we use the compilation [38] of experimental data from Refs.…”

“…We have started our simulations [28] with a simple, purely hadronic EoS [37] which involves only a density dependent mean-field providing saturation of cold nuclear matter at normal nuclear density n 0 = 0.15 fm −3 with the proper binding energy −16 MeV and a certain incompessibility K. It includes 48 lowest mass hadronic states [28]. This EoS is a natural reference point for any other more elaborated EoS.…”

“…[28] we have introduced a 3-fluid dynamical model for simulating heavy-ion collisions in the c.m. energy range √ s N N = 2.3−30 GeV 1 (or E lab = (1−500)A GeV in terms of lab.…”

“…In this paper we would like to present such a study based on simulations within the 3FD model [25,26,28]. In order to estimate the dissipation, we use the approach suggested in Refs.…”

The Compressed Baryonic Matter experiment at FAIR

“…[2]. Right: Energy density versus baryon density in the central cell of Au+Au collisions at various energies from a 3-fluid model [7].…”