Initialization of hydrodynamics in relativistic heavy ion collisions with an energy-momentum transport model

Abstract

A key ingredient of hydrodynamical modeling of relativistic heavy ion collisions is thermal initial conditions, an input that is the consequence of a prethermal dynamics which is not completely understood yet. In the paper we employ a recently developed energy-momentum transport model of the prethermal stage to study influence of the alternative initial states in nucleus-nucleus collisions on flow and energy density distributions of the matter at the starting time of hydrodynamics. In particular, the dependence of the results on isotropic and anisotropic initial states is analyzed. It is found that at the thermalization time the transverse flow is larger and the maximal energy density is higher for the longitudinally squeezed initial momentum distributions. The results are also sensitive to the relaxation time parameter, equation of state at the thermalization time, and transverse profile of initial energy density distribution: Gaussian approximation, Glauber Monte Carlo profiles, etc. Also, test results ensure that the numerical code based on the energy-momentum transport model is capable of providing both averaged and fluctuating initial conditions for the hydrodynamic simulations of relativistic nuclear collisions.

Particle production at energies available at the CERN Large Hadron Collider within an evolutionary model

“…The iHKM parameter values, used in the analysis in the case of T p = 165 MeV, are chosen to be the same as those that have provided the optimal description of multiple LHC bulk observables [16]: τ 0 = 0.1 fm/c, τ th = 1 fm/c, the relaxation time at the pre-thermal stage τ rel = 0.25 fm/c, 0 = 680 GeV/fm 3 , α = 0.24, and the momentum anisotropy of the initial state = 100. For the new particlization temperature T p = 156 MeV most parameter values remain the same, except for 0 = 495 GeV/fm 3 and τ 0 = 0.15 fm/c, which are changed in order to ensure the correct charged particle multiplicity and pion p T spectrum slope.…”

“…As for the possible momentum anisotropy of the parton/gluon initial distribution, typical for the color-glass-condensate-based approaches, it is taken into account by the function f 0 (p) in Eq. (1), which is described in more detail in previous papers [14,16]:…”

“…Once we have defined the initial conditions in the form of a nonthermal energy-momentum tensor, obtained from the distribution (1), we can proceed to the description of the prethermal matter dynamics, using the relaxation time approximation [14,16,17]. This pre-thermal stage starts in iHKM at the initial time τ 0 ≈ 0.1 fm/c, when the initial state is formed, and lasts till the thermalization time τ th = 1 fm/c, when an approximate local thermal equilibrium is supposed to be reached by the initially nonequilibrated system.…”

Bulk observables in Pb+Pb collisions at sNN=5.02TeV at the CERN Large Hadron Collider within the integr

“…According to this requirement, the well-known integrated hydrokinetic model (iHKM) model [1,2] consists of a set of modules/stages, corresponding to a series of successive phases of system's evolution process, including formation of superdense matter, its gradual thermalization, viscous relativistic hydrodynamic expansion as continuous medium, particlization, and the hadronic cascade stage. The "development" of the system at each stage is regulated by specific model parameters, and the aggregated effect of the matter's evolving during all the stages defines the final state of the system and the behavior of various observables, measured in the experiments.…”

Production and Correlations of Strange Mesons and Baryons at RHIC and LHC in Hydrokinetic Model

“…In current section, we present the results of simulations in the integrated hydrokinetic model (iHKM) [26] Also the kaon-pion correlations of various origins, e.g. event-by-event elliptic flow and residual ones, are subject to misinterpretation and may be taken for the K-π bound state.…”