Thermalization, Isotropization and Elliptic Flow from Nonequilibrium Initial Conditions with a Saturation Scale

Abstract

In this article we report on our results about the computation of the elliptic flow of the quark-gluon-plasma produced in relativistic heavy ion collisions, simulating the expansion of the fireball by solving the relativistic Boltzmann equation for the parton distribution function tuned at a fixed shear viscosity to entropy density ratio $\eta /s$. Our main goal is to put emphasis on the role of a saturation scale in the initial gluon spectrum, which makes the initial distribution far from a thermalized one. We find that the presence of the saturation scale reduces the efficiency in building-up the elliptic flow, even if the thermalization process is quite fast ${\tau }_{therm}\approx 0.8fm/c$ and the pressure isotropization even faster ${\tau }_{isotr}\approx 0.3fm/c$. The impact of the non-equilibrium implied by the saturation scale manifests for non-central collisions and can modify the estimate of the viscosity respect to the assumption of full thermalization in $p_T$-space. We find that the estimate of $\eta /s$ is modified from $\eta /s\approx 2/4\pi$ to $\eta /s\approx 1/4\pi$ at RHIC and from $\eta /s\approx 3/4\pi$ to $\eta /s\approx 2/4\pi$ at LHC. We complete our investigation by a study of the thermalization and isotropization times of the fireball for different initial conditions and values of $\eta /s$ showing how the latter affects both isotropization and thermalization. Lastly, we have seen that the range of values explored by the phase-space distribution function $f$ is such that at $p_T<0.5\mathrm{GeV}$ the inner part of the fireball stays with occupation number significantly larger than unity despite the fast longitudinal expansion, which might suggest the possibility of the formation of a transient Bose-Einstein Condensate.

Published version

References in corpus (29)

• Viscosity in Strongly Interacting Quantum Field Theories from Black Hole Physics
• Glauber Modeling in High Energy Nuclear Collisions
• The Color Glass Condensate
• Viscosity Information from Relativistic Nuclear Collisions: How Perfect is the Fluid Observed at RHIC?
• On the Strongly-Interacting Low-Viscosity Matter Created in Relativistic Nuclear Collisions
• Suppression of elliptic flow in a minimally viscous quark-gluon plasma
• Triangular flow in hydrodynamics and transport theory
• Phobos results on charged particle multiplicity and pseudorapidity distributions in Au+Au, Cu+Cu, d+Au, and p+p collisions at ultra-relativistic energies
• Multiplicity scaling in ideal and viscous hydrodynamics
• Has the QCD Critical Point been Signaled by Observations at RHIC ?
• Coalescence Models For Hadron Formation From Quark Gluon Plasma
• Influence of the shear viscosity of the quark-gluon plasma on elliptic flow in ultrarelativistic heavy-ion collisions
• Effects of fluctuations on the initial eccentricity from the Color Glass Condensate in heavy ion collisions
• Azimuthal correlations of forward di-hadrons in d+Au collisions at RHIC in the Color Glass Condensate
• Perturbative QCD Calculations of Elliptic Flow and Shear Viscosity in Au+Au Collisions at $\sqrt{s_{NN}}=200$ GeV
• Single Inclusive Hadron Production at RHIC and the LHC from the Color Glass Condensate
• The eccentricity in heavy-ion collisions from Color Glass Condensate initial conditions
• Eccentricity fluctuations from the Color Glass Condensate at RHIC and LHC
• The applicability of causal dissipative hydrodynamics to relativistic heavy ion collisions
• Hadron spectra and elliptic flow for 200 A GeV Au+Au collisions from viscous hydrodynamics coupled to a Boltzmann cascade
• Eccentricity fluctuation effects on elliptic flow in relativistic heavy ion collisions
• Scalings of Elliptic Flow for a Fluid at Finite Shear Viscosity
• Universality of the saturation scale and the initial eccentricity in heavy ion collisions
• Elliptic flow of gluon matter in ultrarelativistic heavy-ion collisions
• Spectra and elliptic flow for identified hadrons in 2.76 A TeV Pb+Pb collisions
• QCD Viscosity to Entropy Density Ratio in the Hadronic Phase
• Elliptic flow in Pb+Pb collisions at sqrt{s_{NN}} = 2.76 TeV: hybrid model assessment of the first data
• Thermalization of a color glass condensate and review of the "Bottom-Up" scenario
• Kinetic evolution of the glasma and thermalization in heavy ion collisions

Cited by in corpus (44)

• Extraction of Heavy-Flavor Transport Coefficients in QCD Matter
• Directed Flow of Charm Quarks as a Witness of the Initial Strong Magnetic Field in Ultra-Relativistic Heavy Ion Collisions
• Toward a solution to the $R_{AA}$ and $v_2$ puzzle for heavy quarks
• Charmed Hadrons from Coalescence plus Fragmentation in relativistic nucleus-nucleus collisions at RHIC and LHC
• Towards the determination of heavy-quark transport coefficients in quark-gluon plasma
• Electric Conductivity from the solution of the Relativistic Boltzmann Equation
• Impact of Glasma on heavy quark observables in nucleus-nucleus collisions at LHC
• Dynamical collisional energy loss and transport properties of on- and off-shell heavy quarks in vacuum and in the Quark Gluon Plasma
• Effect of pre-equilibrium phase on $R_{AA}$ and $v_2$ of heavy quarks in heavy ion collisions
• Initial state fluctuations from mid-peripheral to ultra-central collisions in a event-by-event transport approach
• Azimuthal Anisotropies at High Momentum from Purely Non-Hydrodynamic Transport
• Propagation of heavy baryons in heavy-ion collisions
• Heavy-light flavour correlations of anisotropic flows at LHC energies within event-by-event transport approach
• Hydrodynamization and non-equilibrium Green's functions in kinetic theory
• Photons from the Early Stages of Relativistic Heavy Ion Collisions
• Modelling Early Stages of Relativistic Heavy Ion Collisions: Coupling Relativistic Transport Theory to Decaying Color-electric Flux Tubes
• Relativistic Boltzmann transport approach with Bose-Einstein statistics and the onset of gluon condensation
• Directed flow of D mesons at RHIC and LHC: non-perturbative dynamics, longitudinal bulk matter asymmetry and electromagnetic fields
• Heavy quark diffusion in pre-equilibrium stage of heavy ion collisions
• Study of collective anisotropies $v_2$ and $v_3$ and their fluctuations in $pA$ collisions at LHC within a relativistic transport approach
• Initial state and thermalization in the Color Glass Condensate framework
• Electromagnetic fields and directed flow in large and small colliding systems at ultrarelativistic energies
• Quarks Production in the Quark-Gluon Plasma Created in Relativistic Heavy Ion Collisions
• Charm and Bottom Hadrons in Hot Hadronic Matter
• Multi-charmed and singled charmed hadrons from coalescence: yields and ratios in different collision systems at LHC
• Collision energy dependence of elliptic flow splitting between particles and their antiparticles from an extended multiphase transport model
• Dissipative hydrodynamics of relativistic shock waves in a Quark Gluon Plasma: comparing and benchmarking alternate numerical methods
• Impact of off-shell dynamics on the transport properties and the dynamical evolution of Charm Quarks at RHIC and LHC temperatures
• Heavy-Flavour Jets in High-Energy Nuclear Collisions
• Bose-Einstein condensation and non-extensive statistics
• The impact of glasma on heavy flavor azimuthal correlations and spectra
• The signature of charge dependent directed flow observables by electromagnetic fields in heavy ion collisions
• Volume effects on the QCD critical end point from thermal fluctuations within the super statistics framework
• Fluctuations of topological charge and chiral density in the early stage of high energy nuclear collisions
• Thermalization of anisotropic quark-gluon plasma produced by decays of color flux tubes
• Transport properties from Charm to Bottom: $p_T$ suppression, anisotropic flow $v_n$ and their correlations to the bulk dynamics
• Pion transverse-momentum spectrum, elliptic flow, and Hanbury-Brown-Twiss interferometry in a viscous granular source model
• A comparative study of different approaches for heavy quark energy loss, based on the latest experimental data
• The Extraordinary Glow
• Directed flow of D and B mesons in an electrically and chirally conductive QGP at LHC energies
• Heavy quark dynamics within a Boltzmann transport model: radiative vs collisional energy loss
• Event shape Engineering analysis of D meson in ultrarelativistic heavy ion collisions
• The quest for the quark-gluon plasma from the perspective of dynamical models of relativistic heavy-ion collisions
• Impact of momentum-dependent drag coefficient on energy loss of charm and bottom quarks in QGP