1,357 research outputs found
Review of the "Bottom-Up" scenario
Thermalization of a longitudinally expanding color glass condensate with
Bjorken boost invariant geometry is investigated within parton cascade BAMPS.
Our main focus lies on the detailed comparison of thermalization, observed in
BAMPS with that suggested in the Bottom-Up scenario. We demonstrate that the
tremendous production of soft gluons via , which is shown in the
Bottom-Up picture as the dominant process during the early preequilibration,
will not occur in heavy ion collisions at RHIC and LHC energies, because the
back reaction hinders the absolute particle multiplication.
Moreover, contrary to the Bottom-Up scenario, soft and hard gluons thermalize
at the same time. The time scale of thermal equilibration in BAMPS calculations
is of order \as^{-2} (\ln \as)^{-2} Q_s^{-1}. After this time the gluon
system exhibits nearly hydrodynamic behavior. The shear viscosity to entropy
density ratio has a weak dependence on and lies close to the lower bound
of the AdS/CFT conjecture.Comment: Quark Matter 2008 Proceeding
Thermalization of gluon matter including gg<->ggg interactions
Within a pQCD inspired kinetic parton cascade we simulate the space time
evolution of gluons which are produced initially in a heavy ion collision at
RHIC energy. The inelastic gluonic interactions do
play an important role: For various initial conditions it is found that
thermalization and the close to ideal fluid dynamical behaviour sets in at very
early times. Special emphasis is put on color glass condensate initial
conditions and the `bottom up thermalization' scenario. Off-equilibrium processes make up the very beginning of the evolution leading to an initial
decrease in gluon number and a temporary avalanche of the gluon momentum
distribution to higher transversal momenta.Comment: 6 pages, 8 figures, Talk given at International Conference on Strong
and Electroweak Matter (SEWM 2006), BNL, New York, May 200
Jet quenching and elliptic flow at RHIC and LHC within a pQCD-based partonic transport model
Fully dynamic simulations of heavy ion collisions at RHIC and at LHC energies
within the perturbative QCD-based partonic transport model BAMPS (Boltzmann
Approach to Multi-Parton Scatterings) are presented, focusing on the
simultaneous investigation of jet quenching and elliptic flow. The model
features inelastic 2 3 processes based on the Gunion-Bertsch matrix element
and has recently been extended to include light quark degrees of freedom,
allowing for direct comparison to hadronic data on the nuclear modification
factor via a fragmentation scheme for high-pT partons. The nuclear modification
factor of neutral pions in central Au+Au collisions at RHIC energy is compared
to experimental data. Furthermore first results on the nuclear modification
factor and the integrated elliptic flow of charged hadrons in Pb+Pb collisions
at LHC are presented and compared to recent ALICE data. These investigations
are complemented by a study on the suppression of D-mesons at LHC based on
elastic interactions with the medium.Comment: To appear in the proceedings of Quark Matter 201
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