2005/02/18 by Berndt Muller, B. Müller, Krishna Rajagopal · 4 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #High-Energy Particle Collisions Research #hep-ph #nucl-ex #nucl-th
paper · pdf · doi:10.1140/epjc/s2005-02256-3
published as Eur.Phys.J.C43:15-21,2005 · 11 pages, 1 figure, JHEP style
arxiv created 2005/02/18 · openalex publication_date 2005/05/30 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The challenge of demonstrating that the matter produced in heavy ion collisions is a deconfined quark-gluon plasma, as predicted by lattice QCD calculations, is the challenge of measuring the number of thermodynamic degrees of freedom ν~ ε/T4 at the time t0 at which the matter comes into approximate local thermal equilibrium and begins to behave like a hydrodynamic fluid. Data from experiments done at the Relativistic Heavy Ion Collider have been used to estimate t0 and to put a lower bound on the energy density ε(t0). However, measuring νhas seemed out of reach, because no current data serve even as qualitative proxies for the temperature T(t0). We point out that νmay equally appropriately be defined via ν~s4/epsilon3, where s is the entropy density, which can be estimated from the measured final state entropy. This estimate is based on the testable assumption of an isentropic expansion. The observation of jet quenching has the potential to provide an upper bound on the energy density at early times. Our goal is to motivate such an analysis by pointing out that it would set a lower bound on ν.