scholarly journals Nonequilibrium Process in the σ Model and Chemical Relaxation Time in a Homogeneous Pionic Gas

1997 ◽  
Vol 50 (1) ◽  
pp. 3
Author(s):  
Mitsuru Ishii
Keyword(s):  
Relaxation Time ◽  
Initial Conditions ◽  
Early Stage ◽  
Local Equilibrium ◽  
Heavy Ion ◽  
Nonequilibrium Process ◽  
Ion Collisions ◽  
System A ◽  
Chemical Relaxation ◽  
S Model

In a homogeneous pionic gas system, a chemical nonequilibrium process is understood to have an effect in the expansion processes that are realized immediately after heavy ion collisions. The chemical relaxation time is calculated by incorporating the π+π↔π +π +π+π reaction, which is given in the second order of perturbation in the s model. The π+π↔π +π +π+π reaction is assumed to be less frequent than the π+π↔π +π scattering that is expected to establish the local equilibrium, and the hydrodynamical equation is solved for various initial conditions. It is shown that the relaxation time is of the order of 100 fm and does not have a significant effect on the expansion process, which implies that the pion number freezeout takes place at an early stage of the expansion.

Study the early stage of heavy ion collisions with direct photons

2014 ◽  
Vol 29 ◽  
pp. 1460230 ◽  
Author(s):  
Fu-Ming Liu ◽  
Sheng-Xu Liu
Keyword(s):  
Collective Motion ◽  
Early Stage ◽  
Heavy Ion ◽  
Gluon Plasma ◽  
Transverse Momentum Spectrum ◽  
Direct Photons ◽  
Ion Collisions ◽  
Phenix Collaboration ◽  
Early Beginning ◽  
Hadronic Data

Based on the modelling of the collective motion in AuAu collisions at [Formula: see text] at centrality 0-20% and 20-40% and PbPb collisions at [Formula: see text] at centrality 0-40% with a 3+1D event-averaged ideal hydrodynamics constrained with hadronic data, we study the transverse momentum spectrum and elliptic flow of direct photons and find that the recent direct photon data from both PHENIX collaboration at RHIC and ALICE collaboration at LHC favour an early beginning of collective expansion (τ0 < 0.6 fm/c) and a late formation of quark gluon plasma (τ ~ 2 fm/c).

scholarly journals Aspects of Relativistic Heavy-Ion Collisions

Universe ◽  
2020 ◽  
Vol 6 (5) ◽  
pp. 61 ◽  
Author(s):  
Georg Wolschin
Keyword(s):  
Heavy Ion Collisions ◽  
Initial Conditions ◽  
Hadron Collider ◽  
Heavy Ion ◽  
Charged Hadron ◽  
Distribution Functions ◽  
Relativistic Heavy Ion Collisions ◽  
Short Time Scale ◽  
Relativistic Heavy Ion Collider ◽  
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 ≤ 1 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 N N ) . 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 s N N = 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.

scholarly journals Fluctuating Glasma Initial Conditions and Flow in Heavy Ion Collisions

2012 ◽  
Vol 108 (25) ◽  
Author(s):  
Björn Schenke ◽  
Prithwish Tribedy ◽  
Raju Venugopalan
Keyword(s):  
Heavy Ion Collisions ◽  
Initial Conditions ◽  
Heavy Ion ◽  
Ion Collisions
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