Hydrodynamic modeling of the deconfinement phase transition in heavy-ion collisions in the NICA–FAIR energy domain

Abstract

We use (3+1) dimensional ideal hydrodynamics to describe the space-time evolution of strongly interacting matter created in Au+Au and Pb+Pb collisions. The model is applied for the domain of bombarding energies 1-160 AGeV which includes future NICA and FAIR experiments. Two equations of state are used: the first one corresponding to resonance hadron gas and the second one including the deconfinement phase transition. The initial state is represented by two Lorentzboosted nuclei. Dynamical trajectories of matter in the central box of the system are analyzed.They can be well represented by a fast shock-wave compression followed by a relatively slow isentropic expansion. The parameters of collective flows and hadronic spectra are calculated under assumption of the isochronous freeze-out. It is shown that the deconfinement phase transition leads to broadening of proton rapidity distributions, increase of elliptic flows and formation of the directed antiflow in the central rapidity region. These effects are most pronounced at bombarding energies around 10 AGeV, when the system spends the longest time in the mixed phase. From the comparison with three-fluid calculations we conclude that the transparency effects are not so important in central collisions at NICA-FAIR energies (below 30 AGeV).

Thermodynamically anomalous regions as a mixed phase signal

“…The hadronic phase of the aforementioned EOS was described by the Walecka model [27] and by a few of its more realistic phenomenological generalizations [17,28,29]. The appearance of anomalous thermodynamic properties for a fast cross-over can be understood similarly, if one formally considers the cross-over states as a kind of mixed phase (but without sharp phase boundary), in which, however, none of the pure phases is able to completely dominate.…”

“…On the basis of these arguments one can understand the reason why the boundary of the mixed phase and QGP corresponds to a local minimum of the X variable along the RHT (shown in Fig. 3) or generalized shock adiabat and why it is also a minimum of X as function of collision energy [15][16][17]29].…”

“…3) which include states in the mixed and the QGP phases. This is a model of W-kind [17,27,29] and its RHT adiabat in the instability region should be replaced by the generalized shock adiabat [15][16][17]. In the region of instability the shock wave for W-kind models has to be replaced by the following hydrodynamic solution [15]: a shock between states O and A 2 (on the RHT adiabat shown in Fig.…”

Strangeness production in heavy-ion collisions

“…The first assumption relies on the hypothesis that after the collision process the wounded nuclei go away from the collision point with velocity close to c, leaving a system with vanishing baryon density. It is extremely difficult to evaluate the initial conditions of the evolving system, but recent works suggest that the early system has a non-negligible baryon density [7], [8]. Concerning the second assumption, the SMES seems to give realistic masses only to the strange degrees-of-freedom, but, especially at low energies, the temperatures reached by the system in the confined state are not large enough to neglect the masses of the lightest non-strange particles.…”

“…Several Hadron Resonance Gas Models have been developed to explain the particle production in heavy-ion physics, achieving good results also for the interpretation of the horn ( [10], [8] and [2]). The particle production in heavy-ion collision is described as a thermal hadron production at the freeze-out stage.…”