Rapidity equilibration in d + Au and Au + Au systems

In a Relativistic Diffusion Model (RDM), the evolution of net-proton rapidity spectra with sqrt(s_NN) in heavy systems is proposed as an indicator for local equilibration and longitudinal expansion. The broad midrapidity valley recently discovered at RHIC in central Au + Au collisions at sqrt(s_NN)= 200 GeV suggests rapid local equilibration which is most likely due to deconfinement, and fast longitudinal expansion. Rapidity spectra of produced charged hadrons in d + Au and Au + Au systems at RHIC energies and their centrality dependence are well described in a three-sources RDM. In central collisions, about 19 % of the produced particles are in the equilibrated midrapidity region for d + Au.Comment: 10 pages, 4 figures; QGPTH05 Vienna; references update

Produced charged hadrons in central Pb + Pb collisions at LHC energies in the RDM

The energy dependence of charged-hadron production in relativistic heavy-ion collisions is investigated in a nonequilibrium-statistical relativistic diffusion model (RDM) with three sources. Theoretical pseudorapidity distributions are compared with Au + Au data at RHIC energies of sqrt(s_NN) = 0.13 and 0.2 TeV, and computed for Pb + Pb central collisions at LHC energies of 2.76 and 5.52 TeV. The central, nearly equilibrated source arising from gluon-gluon collisions becomes the major origin of particle production at LHC energies. The midrapidity dip is determined by the interplay of the three sources.Comment: 19 pages, 4 figures, 1 table; References updated, misprints correcte

Aspects of relativistic heavy-ion collisions

The rapid thermalization of quarks and gluons in the initial stages of relativistic heavy-ion collisions is treated using analytic solutions of a nonlinear diffusion equation with schematic initial conditions, and for gluons with boundary conditions at the singularity. On a similarly short time scale of $t \le1$ fm/$c$, the stopping of baryons is accounted for through a QCD-inspired approach based on the parton distribution functions of valence quarks, and gluons. Charged-hadron production is considered phenomenologically using a linear relativistic diffusion model with two fragmentation sources, and a central gluonic source that rises with $\ln^3(s_{NN})$. The limiting-fragmentation conjecture that agrees with data at energies reached at the Relativistic Heavy Ion Collider (RHIC) is found to be consistent with Large Hadron Collider (LHC) data for Pb-Pb at $\sqrt{s_{NN}}= 2.76$ and $5.02$ TeV. Quarkonia are used as hard probes for the properties of the quark-gluon plasma (QGP) through a comparison of theoretical predictions with recent CMS, ALICE and LHCb data for Pb-Pb and p-Pb collisions.Comment: 19 pages, 19 figure

Local Thermalization in the d + Au System

The extent of a locally equilibrated parton plasma in d + Au collisions at sqrt(s_NN) = 200 GeV is investigated as a function of collision centrality in a nonequilibrium-statistical framework. Based on a three-sources model, analytical solutions of a relativistic diffusion equation are in precise agreement with recent data for charged-particle pseudorapidity distributions. The moving midrapidity source indicates the size of the local thermal equilibrium region after hadronization. In central d + Au collisions it contains about 19% of the produced particles, and its relative importance rises with decreasing centrality.Comment: 9 pages, 3 figures; new tabl

Time evolution of relativistic d + Au and Au + Au collisions

The evolution of charged-particle production in collisions of heavy ions at relativistic energies is investigated as function of centrality in a nonequilibrium-statistical framework. Precise agreement with recent d + Au and Au + Au data at sqrt(s_NN) = 200 GeV is found in a Relativistic Diffusion Model with three sources for particle production. Only the midrapidity source comes very close to local equilibrium, whereas the analyses of the overall pseudorapidity distributions show that the systems remain far from statistical equilibrium.Comment: 16 pages, 5 figures, 1 tabl