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Primordial hadrosynthesis in the Little Bang
| Content Provider | Semantic Scholar |
|---|---|
| Author | Heinz, Ulrich |
| Copyright Year | 1999 |
| Abstract | The present status of soft hadron production in high energy heavy-ion collisions is summarized. In spite of strong evidence for extensive dynamical evolution and collective expansion of the fireball before freeze-out I argue that its chemical composition is hardly changed by hadronic final state interactions. The measured hadron yields thus reflect the primordial conditions at hadronization. The observed production pattern is consistent with statistical hadronization at the Hagedorn temperature from a state of uncorrelated, color deconfined quarks and antiquarks, but requires non-trivial chemical evolution of the fireball in a prehadronic (presumably QGP) stage before hadron formation. 1. Heavy-ion data and the nuclear phase diagram Relativistic heavy-ion collisions are studied with the goal of creating hot and dense hadronic matter and to investigate the nuclear phase diagram at high temperatures and densities, including the expected phase transition to a color deconfined quark-gluon plasma. But even if the energy deposited in the reaction zone is quickly randomized and the fireball constituents reach an approximate state of local thermal equilibrium, a simple connection between heavy-ion observables and the phase diagram is still not easy: the pressure generated by the thermalization process blows the fireball apart, causing a strong time dependence of its thermodynamic conditions which is difficult to unfold from the experimental observations. There are therefore two fundamental issues to be solved before one can extract information on the nuclear phase diagram from heavy-ion experiments: (1) To what degree does the fireball approach local thermal equilibrium? (2) Which ob-servables are sensitive to which stage(s) of its dynamical evolution, and which is the most reliable procedure for extracting the corresponding thermodynamic information? Combining microscopic models for the dynamical fireball evolution with macroscopic thermal models for the analysis of heavy-ion data, significant progress has been recently made in answering both of these questions. Crucial for this achievement was the dramatically improved quantity and quality of hadron production data from the analysis of collisions between very heavy nuclei (Au+Au, Pb+Pb) from SIS to SPS. Fig. 1 shows a compilation by Cleymans and Redlich [1] of hadronic freeze-out points in the nuclear phase diagram from various collision systems and beam energies. The upper set of points, parametrized by a constant average energy per particle E/N=1 GeV [1], is obtained from measured hadron yields. They indicate the average thermodynamic conditions at chemical freeze-out when the hadron abundances stopped evolving. The lower |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://arxiv.org/pdf/nucl-th/9907060v1.pdf |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | AICARDI-GOUTIERES SYNDROME 1 Apollo Abort Guidance System Approximation algorithm BANG file Beneath a Steel Sky Compiler Coupling (computer programming) Dynamical system Energy, Physics Equilibrium Experiment IBM 1401 Symbolic Programming System Interaction Ions Kinetic Monte Carlo Kinetics Large Hadron Collider Lattice QCD Nucleons Observable PDGFB wt Allele Phase Transition Phase diagram Plasma Active Radial (radio) Randomized algorithm SEPHS1 gene SPS Small Thermodynamics collision density slope |
| Content Type | Text |
| Resource Type | Article |
