795 research outputs found
Thermal photons from fluctuating initial conditions
Event-by-event fluctuations of initial QCD-matter density produced in
heavy-ion collisions at RHIC enhance the production of thermal photons
significantly in the region GeV/ compared to a smooth
initial-state averaged profile in the ideal hydrodynamic calculation. This
enhancement is a an early time effect due to the presence of hotspots or
over-dense regions in the fluctuating initial state. The effect of fluctuations
is found to be stronger in peripheral than in central collisions.Comment: 4 pages, 3 figures. Talk given at Quark Matter 2011, 22-28 May 2011,
Annecy, Franc
Elliptic flow from event-by-event hydrodynamics
We present an event-by-event hydrodynamical framework which takes into
account the initial density fluctuations arising from a Monte Carlo Glauber
model. The elliptic flow is calculated with the event plane method and a
one-to-one comparison with the measured event plane is made. Both the
centrality- and -dependence of the are remarkably well reproduced.
We also find that the participant plane is a quite good approximation for the
event plane.Comment: 4 pages, 3 figures. Talk given at Quark Matter 2011, 22-28 May 2011,
Annecy, Franc
Systematics of parton-medium interaction from RHIC to LHC
Despite a wealth of experimental data for high-P_T processes in heavy-ion
collisions, discriminating between different models of hard parton-medium
interactions has been difficult. A key reason is that the pQCD parton spectrum
at RHIC is falling so steeply that distinguishing even a moderate shift in
parton energy from complete parton absorption is essentially impossible. In
essence, energy loss models are effectively only probed in the vicinity of zero
energy loss and, as a result, at RHIC energies only the pathlength dependence
of energy loss offers some discriminating power. At LHC however, this is no
longer the case: Due to the much flatter shape of the parton p_T spectra
originating from 2.76 AGeV collisions, the available data probe much deeper
into the model dynamics. A simultaneous fit of the nuclear suppression at both
RHIC and LHC energies thus has great potential for discriminating between
various models that yield equally good descriptions of RHIC data alone.Comment: Talk given at Quark Matter 2011, 22-28 May 2011, Annecy, Franc
Initial state anisotropies and their uncertainties in ultrarelativistic heavy-ion collisions from the Monte Carlo Glauber model
In hydrodynamical modeling of heavy-ion collisions, the initial-state spatial
anisotropies are translated into momentum anisotropies of the final-state
particle distributions. Thus, understanding the origin of the initial-state
anisotropies and their uncertainties is important before extracting specific
QCD matter properties, such as viscosity, from the experimental data. In this
work we review the wounded nucleon approach based on the Monte Carlo Glauber
model, charting in particular the uncertainties arising from modeling of the
nucleon-nucleon interactions between the colliding nucleon pairs and
nucleon-nucleon correlations inside the colliding nuclei. We discuss the
differences between the black disk model and a probabilistic profile function
approach for the inelastic nucleon-nucleon interactions, and investigate the
influence of initial-state correlations using state-of-the-art modeling of
these.Comment: 9 pages, 6 figure
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