Article

Influence of a temperature-dependent shear viscosity on the azimuthal asymmetries of transverse momentum spectra in ultrarelativistic heavy-ion collisions

Physical Review C (Impact Factor: 3.88). 03/2012; 86(1). DOI: 10.1103/PhysRevC.86.014909
Source: arXiv

ABSTRACT We study the influence of a temperature-dependent shear viscosity over
entropy density ratio $\eta/s$, different shear relaxation times $\tau_\pi$, as
well as different initial conditions on the transverse momentum spectra of
charged hadrons and identified particles. We investigate the azimuthal flow
asymmetries as a function of both collision energy and centrality. The elliptic
flow coefficient turns out to be dominated by the hadronic viscosity at RHIC
energies. Only at higher collision energies the impact of the viscosity in the
QGP phase is visible in the flow asymmetries. Nevertheless, the shear viscosity
near the QCD transition region has the largest impact on the collective flow of
the system. We also find that the centrality dependence of the elliptic flow is
sensitive to the temperature dependence of $\eta/s$.

1 Bookmark
 · 
58 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigate the applicability of fluid dynamics in ultrarelativistic heavy ion (AA) collisions and high multiplicity proton nucleus (pA) collisions. In order for fluid dynamics to be applicable the microscopic and macroscopic distance/time scales of the system have to be sufficiently separated. The degree of separation is quantified by the ratio between these scales, usually referred to as the Knudsen number. In this work, we calculate the Knudsen numbers reached in fluid dynamical simulations of AA and pA collisions at RHIC and LHC energies. For this purpose, we consider different choices of shear viscosity parametrizations, initial states and initialization times. We then estimate the values of shear viscosity for which the fluid dynamical description of ultrarelativistic AA and pA collisions breaks down. In particular, we study how such values depend on the centrality, in the case of AA collision, and multiplicity, in the case of pA collision. We found that the maximum viscosity in AA collisions is of the order $\eta/s \sim 0.1 \ldots 0.2$, which is similar in magnitude to the viscosities currently employed in simulations of heavy ion collisions. For pA collisions, we found that such limit is significantly lower, being less than $\eta/s=0.08$
    04/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this proceedings contribution I review recent progress in our understanding of the bulk dynamics of relativistic systems that possess potentially large local rest frame momentum-space anisotropies. In order to deal with these momentum-space anisotropies, a reorganization of relativistic viscous hydrodynamics can been made around an anisotropic background, and the resulting dynamical framework has been dubbed "anisotropic hydrodynamics." I also discuss expectations for the degree of momentum-space anisotropy of the quark gluon plasma generated in relativistic heavy ion collisions at RHIC and LHC from second-order viscous hydrodynamics, strong-coupling approaches, and weak-coupling approaches.
    Nuclear Physics A 01/2014; · 2.50 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The introduced earlier projection method for boost-invariant and cylindrically symmetric systems is used to introduce a new formulation of anisotropic hydrodynamics that allows for three substantially different values of pressure acting locally in three different directions. Our considerations are based on the Boltzmann kinetic equation with the collision term treated in the relaxation time approximation and the momentum anisotropy is included explicitly in the leading term of the distribution function. A novel feature of our work is the complete analysis of the second moment of the Boltzmann equation, in addition to the zeroth and first moments that have been analyzed in earlier studies. We define the final equations of anisotropic hydrodynamics in the leading order as a subset of the analyzed moment equations (and their linear combinations) which agree with the Israel-Stewart theory in the case of small pressure anisotropies.
    Physical Review C 12/2013; 89(3). · 3.88 Impact Factor

Full-text (2 Sources)

Download
8 Downloads
Available from
May 29, 2014