QCD PHASE TRANSITION STUDIED BY MEANS OF HADRON PRODUCTION

摘要

We address the hadronization process of a QGP fireball formed in relativistic heavy-ion collisions in the entire range of past and present heavy-ion collision reaction energies. A precise method of analysis of hadron multiplicities has evolved into the "SHARE with CHARM" statistical hadronization model. Using this tool, we successfully describe -over many orders of magnitude - the yield of all hadrons produced in the full range of reaction energies and centralities; exceptions are peripheral and more central collisions at low energies. The properties of the fireball final state can be understood by considering all primary hadronic particles. The dense hadron fireball created at SPS, RHIC, and LHC shows the final state differentiated solely by: ⅰ) volume changes; and ⅱ) strangeness, (charm) flavor content. A universal hadronization pressure P = (80 ± 3) MeV/fm~3 is found. The strangeness content of a large fireball, as compared to entropy, shows the presence of quark-gluon plasma degrees of freedom near the chemical QGP equilibrium. The "Universal Hadronization" condition common to SPS, RHIC, and LHC agrees with the proposed direct QGP fireball evaporation into free-streaming hadrons. Looking ahead, we discuss qualitatively how heavy-flavor production contributes to energy stopping in the central rapidity region as function of reaction energy: the cases of LHC at full energy and future super-LHC.