4,770 research outputs found
Elliptic flow of gluon matter in ultrarelativistic heavy-ion collisions
Employing a perturbative QCD based parton cascade we calculate the elliptic
flow and its transverse momentum dependence for the gluon
matter created in Au+Au collisions at GeV. To make
comparisons with the experimental data at the BNL Relativistic Heavy Ion
Collider (RHIC), parton-hadron duality is assumed. We find that whereas the
integrated matches the experimental data, the gluon (or pion)
is about 20-50% smaller than the experimental data. Hadronization via gluon
fragmentation and quark recombination seems to be the key to explaining the
necessary jump of from the partonic to the hadronic phase. We also
show that the elliptic flow values moderately depend on the chosen freezeout
condition, which will thus constrain the shear viscosity to the entropy density
ratio of the quark gluon plasma created at RHIC.Comment: 20 pages, 7 figures, minor corrections, published versio
Energy loss in a partonic transport model including bremsstrahlung processes
A detailed investigation of the energy loss of gluons that traverse a thermal
gluonic medium simulated within the perturbative QCD--based transport model
BAMPS (a Boltzmann approach to multiparton scatterings) is presented in the
first part of this work. For simplicity the medium response is neglected in
these calculations. The energy loss from purely elastic interactions is
compared to the case where radiative processes are consistently included based
on the matrix element by Gunion and Bertsch. From this comparison gluon
multiplication processes gg -> ggg are found to be the dominant source of
energy loss within the approach employed here. The consequences for the
quenching of gluons with high transverse momentum in fully dynamic simulations
of Au+Au collisions at the RHIC energy of sqrt(s) = 200 AGeV are discussed in
the second major part of this work. The results for central collisions as
discussed in a previous publication are revisited and first results on the
nuclear modification factor R_AA for non-central Au+Au collisions are
presented. They show a decreased quenching compared to central collisions while
retaining the same shape. The investigation of the elliptic flow v2 is extended
up to non-thermal transverse momenta of 10 GeV, exhibiting a maximum v2 at
roughly 4 to 5 GeV and a subsequent decrease. Finally the sensitivity of the
aforementioned results on the specific implementation of the effective modeling
of the Landau-Pomeranchuk-Migdal (LPM) effect via a formation time based
cut-off is explored.Comment: 40 pages, 20 figures, 1 tabl
Perturbative QCD Calculations of Elliptic Flow and Shear Viscosity in Au+Au Collisions at GeV
The elliptic flow and the ratio of the shear viscosity over the entropy
density, , of gluon matter are calculated from the perturbative QCD
(pQCD) based parton cascade Boltzmann approach of multiparton scatterings. For
Au+Au collisions at A GeV the gluon plasma generates large
values measured at the BNL Relativistic Heavy Ion Collider. Standard pQCD
yields as small as the lower bound found from the
anti-de Sitter/conformal field theory conjecture.Comment: 4 pages, 6 figures, new results added in Figs 1, 2, and 3, version
published in PR
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