Anisotropic transverse flow and the quark-hadron phase transition

Abstract

We use ͑3ϩ1͒-dimensional hydrodynamics with exact longitudinal boost invariance to study the influence of collision centrality and initial energy density on the transverse flow pattern and the angular distributions of particles emitted near midrapidity in ultrarelativistic heavy-ion collisions. We concentrate on radial flow and the elliptic flow coefficient v 2 as functions of the impact parameter and collision energy. We demonstrate that the finally observed elliptic flow is established earlier in the collision than the observed radial flow and thus probes the equation of state at higher energy densities. We point out that a phase transition from hadronic matter to a color-deconfined quark-gluon plasma leads to nonmonotonic behavior in both beam energy and impact parameter dependences which, if observed, can be used to identify such a phase transition. Our calculations span collision energies from the Brookhaven AGS ͑Alternating Gradient Synchrotron͒ to beyond the LHC ͑Large Hadron Collider͒; the QGP phase transition signature is predicted between the lowest available SPS ͑CERN Super Proton Synchrotron͒ and the highest RHIC ͑Brookhaven Relativistic Heavy Ion Collider͒ energies. To optimize the chances for applicability of hydrodynamics we suggest studying the excitation function of flow anisotropies in central uranium-uranium collisions in the side-on-side collision geometry.

Anisotropic flow inCu+Aucollisions atsNN=200GeV

“…The hadron transverse momentum anisotropy is generated by the pressure anisotropy in the initial compressed matter formed in noncentral heavy-ion collisions [2,3] and is sensitive to the properties of produced matter in these collisions. For heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC), it has been shown that this sensitivity exists not only in the larger elliptic flow [4][5][6][7][8][9][10][11] but also in smaller higher order anisotropic flows [12][13][14][15][16][17][18]. To investigate the influence of initial collision geometry on anisotropic flows in heavy-ion collisions, one usually varies the impact parameter of a collision or the atomic number of colliding nuclei [19].…”

Equation of state dependence of Mach cone-like structures in Au+Au collisions

“…To simulate central Au+Au collisions at RHIC, we use the standard initialization described in [31] and provided in the downloaded AZHYDRO input file [32], corresponding to a peak initial energy density of ε i = 30 GeV /f m 3 at τ i = 0.6 f m/c. Since we are exploring the equation of state dependence on the splitting of the away side jet, we assume a simple equation of state, p(ε) = c 2 s ε, with ε(T ) = π 2 30 g q T 4 , g q = 47.5.…”

“…For the hydrodynamic evolution we use a modified version of the publicly available hydrodynamic code AZHY-DRO [31,32]. The code is formulated in (τ, x, y, η) coordinates, where τ = √ t 2 −z 2 is the longitudinal proper time, η= 1 2 ln t+z t−z is space-time rapidity, and r ⊥ = (x, y) defines the plane transverse to the beam direction z. AZHYDRO employs longitudinal boost invariance along z but this is violated by the source term (4).…”

Effect of jet quenching on hydrodynamical evolution of QGP

“…We use the equation of state EOS-Q described in [7,16] incorporating a first order phase transition and hadronic chemical freeze-out at a critical temperature T c = 164 MeV. The hadronic sector of EOS-Q is soft with a squared speed of sound c 2 s ≈ 0.15.…”

“…To simulate central Au+Au collisions at RHIC, we use the standard initialization described in [7] and provided in the downloaded AZHYDRO input file [16], corresponding to a peak initial energy density of ε 0 = 30 GeV/fm 3 at τ 0 = 0.6 fm/c. We use the equation of state EOS-Q described in [7,16] incorporating a first order phase transition and hadronic chemical freeze-out at a critical temperature T c = 164 MeV.…”