168 research outputs found
Initial condition for hydrodynamics, partonic free streaming, and the uniform description of soft observables at RHIC
We investigate the role of the initial condition used for the hydrodynamic
evolution of the system formed in ultra-relativistic heavy-ion collisions and
find that an appropriate choice motivated by the models of early-stage
dynamics, specifically a simple two-dimensional Gaussian profile, leads to a
uniform description of soft observables measured in the Relativistic Heavy-Ion
Collider (RHIC). In particular, the transverse-momentum spectra, the
elliptic-flow, and the Hanbury-Brown--Twiss correlation radii, including the
ratio R_out/R_side as well as the dependence of the radii on the azimuthal
angle (azHBT), are properly described. We use the perfect-fluid hydrodynamics
with a realistic equation of state based on lattice calculations and the
hadronic gas at high and low temperatures, respectively. We also show that the
inclusion of the partonic free-streaming in the early stage allows to delay the
start of the hydrodynamical description to comfortable times of the order of 1
fm/c. Free streaming broadens the initial energy-density profile, but generates
the initial transverse and elliptic flow. The data may be described equally
well when the hydrodynamics is started early, or with a delay due to partonic
free-streaming.Comment: 4 pages, 4 figure
Hydrodynamic predictions for Pb+Pb collisions at 2.76 TeV
Using the newest data for pp scattering at the CERN Large Hadron Collider
(LHC) combined with the Glauber model, we make hydrodynamic predictions for the
soft hadronic observables planned to be measured in the forthcoming Pb+Pb
collisions at 2.76 TeV
Size fluctuations of the initial source and the event-by-event transverse momentum fluctuations in relativistic heavy-ion collisions
We show that the event-by-event fluctuations of the transverse size of the
initial source, which follow directly from the Glauber treatment of the
earliest stage of relativistic heavy-ion collisions, cause, after hydrodynamic
evolution, fluctuations of the transverse flow velocity at hadronic freeze-out.
This in turn leads to event-by-event fluctuations of the average transverse
momentum, p_T. Simulations with GLISSANDO for the Glauber phase, followed by a
realistic hydrodynamic evolution and statistical hadronization carried out with
THERMINATOR, lead to agreement with the RHIC data. In particular, the magnitude
of the effect, its centrality dependence, and the weak dependence on the
incident energy are properly reproduced. Our results show that bulk of the
observed event-by-event p_T fluctuations may be explained by the fluctuations
of the size of the initial source.Comment: 5 pages, 4 figures, version accepted in PR
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