Temperature dependence of transport coefficients of QCD in high-energy heavy-ion collisions

Abstract

Using our developed new relativistic viscous hydrodynamics code, we investigate the temperature dependence of shear and bulk viscosities from comparison with the ALICE data: single particle spectra and collective flows of Pb+Pb √ sNN = 2.76 TeV collisions at the Large Hadron Collider. We find that from the comprehensive analyses of centrality dependence of single particle spectra and collective flows, we can extract detailed information on the quark-gluon plasma bulk property, without the information being smeared by the final state interactions. I. INTRODUCTIONSince the success of production of strongly interacting quark-gluon plasma (QGP) at the Relativistic Heavy Ion Collider (RHIC) [1], a relativistic viscous hydrodynamic model has been widely used for the description of spacetime evolution of the hot and dense matter created after collisions. Now at RHIC as well as at the Large Hadron Collider (LHC) high-energy heavy-ion collisions are performed and many experimental data are reported. Because the relativistic viscous hydrodynamic equation has close a relation to an equation of state (EoS) and transport coefficients of the QCD matter, analyses of experimental data at RHIC and the LHC based on a relativistic viscous hydrodynamic model can provide an insight into the detailed information on the QGP bulk property.The recent development of a lattice QCD calculation for the EoS at vanishing chemical potential is remarkable. Two groups, the Wuppertal-Budapest and HotQCD Collaborations, report almost the same (pseudo)critical temperatures, T c = 155 ± 6 MeV [2] and T c = 154 ± 9 MeV [3], respectively. On the other hand, the evaluation of the shear viscosity to entropy density ratio η/s of the hadronic phase and the QGP phase is investigated based on the Boltzmann equation [4,5]. Due to the existence of the Kovtun-Son-Starinets (KSS) bound, the lower bound of η/s [6], η/s takes the minimum around the critical temperature [7]. On the other hand, the behavior of temperature dependence of the bulk viscosity to entropy density ratio is not clear. For example, ζ/s of a massive pion gas decreases with temperature [8,9] below the critical temperature. Also, above the critical temperature, ζ/s of quark-gluon matter [10] or gluon plasma [11] decreases with temperature. There is not a conclusive understanding of quantitative information on the transport coefficients of QCD matter.Therefore phenomenological analyses of transport coefficients from comparison with experimental data at RHIC and the LHC are indispensable [12][13][14][15][16][17][18][19]. It turns out that

Hydrodynamic Collectivity and Bulk Properties of QCD Matter in High-Energy Heavy-Ion Collisions

“…We explore transport coefficients of QGP through quantitative analyses of the LHC data, such as one-particle distributions and collective flows in Pb+Pb √ s NN = 2.76 TeV collisions. Here we present highlights of our results [7]. First we determine parameters in the initial condition T R ENTo, using pseudorapidity distributions of charged hadrons at central collision [8,9].…”

Hydrodynamic Expansion and the Collectivity in Small Systems

“…Here we set to be p = 0 which means IP-Glasma. Then we solve the relativistic hydrodynamic equation ∂ µ T µν = 0, employing the new 3+1D relativistic viscous hydrodynamics code in which a Riemann solver and a Piecewise Exact solution method are used [5]. Here T µν is the energy-momentum tensor.…”

“…where the critical temperature T c = 167 MeV, the sound velocity c s , (η/s) min = 0.08, b = 40, c 1 = 10 and c 2 = 0.7 in Ref. [5]. The equation of state used in hydrodynamics simulation is parametrized based on the Lattice QCD calculation and hadron resonance gas [6].…”

Analysis of Small Systems at RHIC Based on 3+1D Relativistic Viscous Hydrodynamic Model

“…Our phenomenological model is composed of the following parts [7]; initial condition, hydrodynamic expansion and a hadron-based event generator, UrQMD [9]. We prepare an initial entropy distribution with using a phenomenological model T R ENTo [4].…”

“…Therefore, yields of strange hadrons play an important role to reveal the property of QGP [3]. We investigate the QGP bulk property in small systems, analyzing the experimental data at RHIC with a phenomenological model in which the state-of-the-art relativistic viscous hydrodynamics code is used [7].…”