22 research outputs found
Mass number scaling in ultra-relativistic nuclear collisions from a hydrodynamical approach
We study the different nucleus-nucleus collisions, O+Au, S+S, S+Ag, S+Au and
Pb+Pb, at the CERN-SPS energy in a one-fluid hydrodynamical approach using a
parametrization based on baryon stopping in terms of the thickness of colliding
nuclei. Good agreement with measured particle spectra is achieved. We deduce
the mass number scaling behaviour of the initial energy density. We find that
the equilibration time is nearly independent of the size of the colliding
nuclei.Comment: 27 pages, figures included, submitted to European Physical Journa
Initial Conditions in the One-Fluid Hydrodynamical Description of Ultrarelativistic Nuclear Collisions
We present a phenomenological model for the initial conditions needed in a one-fluid hydrodynamical description of ultrarelativistic nuclear collisions at CERN-SPS. The basic ingredient is the parametrization of the baryon stopping, i.e. the rapidity distribution, as a function of the thickness of the nuclei. We apply the model to S + S and Pb + Pb collisions and find after hydrodynamical evolution reasonable agreement with the data
Dynamical freeze-out condition in ultrarelativistic heavy ion collisions
We determine the decoupling surfaces for the hydrodynamic description of
heavy ion collisions at RHIC and LHC by comparing the local hydrodynamic
expansion rate with the microscopic pion-pion scattering rate. The pion
spectra for nuclear collisions at RHIC and LHC are computed by applying the
Cooper-Frye procedure on the dynamical-decoupling surfaces, and compared with
those obtained from the constant-temperature freeze-out surfaces. Comparison
with RHIC data shows that the system indeed decouples when the expansion rate
becomes comparable with the pion scattering rate. The dynamical decoupling
based on the rates comparison also suggests that the effective decoupling
temperature in central heavy ion collisions remains practically unchanged from
RHIC to LHC.Comment: 7 pages, 9 figure
Elliptic flow in nuclear collisions at the Large Hadron Collider
We use perfect-fluid hydrodynamical model to predict the elliptic flow
coefficients in Pb + Pb collisions at the Large Hadron Collider (LHC). The
initial state for the hydrodynamical calculation for central collisions
is obtained from the perturbative QCD + saturation (EKRT) model. The centrality
dependence of the initial state is modeled by the optical Glauber model. We
show that the baseline results obtained from the framework are in good
agreement with the data from the Relativistic Heavy Ion Collider (RHIC), and
show predictions for the spectra and elliptic flow of pions in Pb + Pb
collisions at the LHC. Also mass and multiplicity effects are discussed.Comment: 11 pages, 10 figure
Heavy Ion Physics at the LHC with the ATLAS Detector
The ATLAS detector at CERN will provide a high-resolution
longitudinally-segmented calorimeter and precision tracking for the upcoming
study of heavy ion collisions at the LHC (sqrt(s_NN)=5520 GeV). The calorimeter
covers |eta|<5 with both electromagnetic and hadronic sections, while the inner
detector spectrometer covers |eta|<2.5. ATLAS will study a full range of
observables necessary to characterize the hot and dense matter formed at the
LHC. Global measurements (particle multiplicities, collective flow) will
provide access into its thermodynamic and hydrodynamic properties. Measuring
complete jets out to 100's of GeV will allow detailed studies of energy loss
and its effect on jets. Quarkonia will provide a handle on deconfinement
mechanisms. ATLAS will also study the structure of the nucleon and nucleus
using forward physics probes and ultraperipheral collisions, both enabled by
segmented Zero Degree Calorimeters.Comment: 9 pages, 8 figures, submitted to the Proceedings of Quark Matter
2006, Shanghai, China, November 14-20, 200
Temperature dependent sound velocity in hydrodynamic equations for relativistic heavy-ion collisions
We analyze the effects of different forms of the sound-velocity function
cs(T) on the hydrodynamic evolution of matter formed in the central region of
relativistic heavy-ion collisions. At high temperatures (above the critical
temperature Tc) the sound velocity is calculated from the recent lattice
simulations of QCD, while in the low temperature region it is obtained from the
hadron gas model. In the intermediate region we use different interpolations
characterized by the values of the sound velocity at the local maximum (at T =
0.4 Tc) and local minimum (at T = Tc). In all considered cases the temperature
dependent sound velocity functions yield the entropy density, which is
consistent with the lattice QCD simulations at high temperature. Our
calculations show that the presence of a distinct minimum of the sound velocity
leads to a very long (about 20 fm/c) evolution time of the system, which is not
compatible with the recent estimates based on the HBT interferometry. Hence, we
conclude that the hydrodynamic description is favored in the case where the
cross-over phase transition renders the smooth sound velocity function with a
possible shallow minimum at Tc.Comment: 6 pages, 3 figures, talk given at SQM'07 Levoca, Slovaki