Lattice QCD Equation Of State Research Articles

Transport properties of anisotropically expanding quark-gluon plasma within a quasiparticle model

The bulk and shear viscosities ($\eta$ and $\zeta$) have been studied for quark-gluon-plasma produced in relativistic heavy ion collisions within semi-classical transport theory, in a recently proposed quasi-particle model of (2+1)-flavor lattice QCD equation of state. These transport parameters have been found to be highly sensitive to the interactions present in hot QCD. Contributions to the transport coefficients from both the gluonic sector and the matter sector have been investigated. The matter sector is found to be significantly dominating over the gluonic sector, in both the cases of $\eta$ and $\zeta$. The temperature dependences of the quantities, $\zeta/{\mathcal S}$, and $\zeta/\eta$ indicate a sharply rising trend for the $\zeta$, closer to the QCD transition temperature. Both $\eta$, and $\zeta$ are shown to be equally significant for the temperatures that are accessible in the relativistic heavy ion collision experiments, and hence play crucial role while investigating the properties of the quark-gluon plasma.

PRODUCTION OF THERMAL PHOTONS IN A SIMPLE CHIRAL-HYDRODYNAMIC MODEL

We use a self-consistent chiral-hydrodynamic formalism which combines the linear σ model with second-order hydrodynamics in 2 + 1 dimensions to compute the spectrum of thermal photons produced in Au+Au collisions at [Formula: see text]. The temperature-dependent shear viscosity of the model, η, is calculated from the linearized Boltzmann equation. We compare the results obtained in the chiral-hydrodynamic model to those obtained in the second-order theory with a Lattice QCD equation of state and a temperature-independent value of η/s. We find that the thermal photon production is significantly larger in the latter model due to a slower evolution and larger dissipative effects.

Quasiparticle description of (2+1)- flavor lattice QCD equation of state

A quasi-particle model has been employed to describe the $(2+1)$-flavor lattice QCD equation of state with physical quark masses. The interaction part of the equation of state has been mapped to the effective fugacities of otherwise non-interacting quasi-gluons and quasi-quarks. The mapping is found to be exact for the equation of state. The model leads to non-trivial dispersion relations for quasi-partons. The dispersion relations, effective quasi-particle number densities, and trace anomaly have been investigated employing the model.A Virial expansion for the EOS has further been obtained to investigate the role of interactions in quark-gluon plasma (QGP). Finally, Debye screening in QGP has been studied employing the model.

Modeling Quark Gluon Plasma Using CHIMERA

We attempt to model Quark Gluon Plasma (QGP) evolution from the initial Heavy Ion collision to the final hadronic gas state by combining the Glauber model initial state conditions with eccentricity fluctuations, pre-equilibrium flow, UVH2+1 viscous hydrodynamics with lattice QCD Equation of State (EoS), a modified Cooper-Frye freeze-out and the UrQMD hadronic cascade. We then evaluate the model parameters using a comprehensive analytical framework which together with the described model we call CHIMERA. Within our framework, the initial state parameters, such as the initial temperature (Tinit), presence or absence of initial flow, viscosity over entropy density (η/S) and different Equations of State (EoS), are varied and then compared simultaneously to several experimental data observables: HBT radii, particle spectra and particle flow. χ2/nds values from comparison to the experimental data for each set of initial parameters will then used to find the optimal description of the QGP with parameters that are difficult to obtain experimentally, but are crucial to understanding of the matter produced.

Elliptic flow in Pb+Pb collisions atsNN=2.76 TeV: Hybrid model assessment of the first data

We analyze the elliptic flow parameter ${v}_{2}$ in Pb+Pb collisions at $\sqrt{{s}_{\mathit{NN}}}$ $=$ 2.76 TeV and in Au+Au collisions at $\sqrt{{s}_{\mathit{NN}}}=200$ GeV using a hybrid model in which the evolution of the quark gluon plasma is described by ideal hydrodynamics with a state-of-the-art lattice QCD equation of state, and the subsequent hadronic stage by a hadron cascade model. For initial conditions, we employ Monte Carlo versions of the Glauber and the Kharzeev-Levin-Nardi models and compare results with each other. We demonstrate that the differential elliptic flow ${v}_{2}({p}_{T})$ hardly changes when the collision energy increases, whereas the integrated ${v}_{2}$ increases due to the enhancement of mean transverse momentum. The amount of increase of both ${v}_{2}$ and mean ${p}_{T}$ depends significantly on the model of initialization.

Elliptic flow inU+Ucollisions atsNN=200GeV and inPb+Pbcollisions atsNN=2.76TeV: Prediction from a hybrid approach

We predict the elliptic flow parameter v_2 in U+U collisions at sqrt{s_{NN}}=200 GeV and in Pb+Pb collisions at sqrt{s_{NN}} = 2.76 TeV using a hybrid model in which the evolution of the quark gluon plasma is described by ideal hydrodynamics with a state-of-the-art lattice QCD equation of state, and the subsequent hadronic stage by a hadron cascade model.

Quasi-particle model for lattice QCD: quark–gluon plasma in heavy ion collisions

We propose a quasi-particle model to describe the lattice QCD equation of state for pure SU(3) gauge theory in its deconfined state, for T≥1.5T c. The method involves mapping the interaction part of the equation of state to an effective fugacity of otherwise non-interacting quasi-gluons. We find that this mapping is exact. Using the quasi-gluon distribution function, we determine the energy density and the modified dispersion relation for the single particle energy, in which the trace anomaly is manifest. As an application, we first determine the Debye mass, and then the important transport parameters, viz., the shear viscosity, η, and the shear viscosity to entropy density ratio, $\eta/{\mathcal{S}}$ . We find that both η and $\eta/{\mathcal{S}}$ are sensitive to the interactions, and that the interactions significantly lower both η and $\eta/\mathcal{S}$ .

Entropy of expanding QCD matter

Using the lattice QCD equation of state for an isentropically expanding fireball we follow the evolution of the effective number of particles in an ideal gas, Neff=pV/T. This number reduces to its third around the crossover temperature, which helps to resolve the entropy problem inherent in hadronization models assuming quark coalescence.

Equation of state of deconfined matter within a dynamical quasiparticle description

A simple quasiparticle model, motivated by lowest-order perturbative QCD, is proposed. It is applied to interpret the lattice QCD equation of state. A reasonable reproduction of the lattice data is obtained. In contrast to existing quasiparticle models, the present model is formulated in dynamical rather than thermodynamical terms, and is easily applicable to a system with finite baryon density. In particular, the model simulates the confinement property.