Hadronization as valon confinement in the course of nuclear-matter cooling

Abstract

The updated three-phase concept of nuclear-matter evolution in the course of cooling—from a quark-qluon plasma (QGP) through an intermediate phase involving massive constituent quarks Q (valons), pions, and kaons (QπK) to hadronic matter (H)—is exploited to describe relative hadronic yields from the midrapidity region in heavy-ion collisions at high energies. Attention is given primarily to the QπK phase, which is argued to permit a correct description within the ideal-gas approximation. This phase must exist until the mean spacing between valons approaches the confinement radius (at the temperature of T _H-115±10 MeV), in which case valons begin fusing to form final hadrons. The hadronic yields obtained by means of a thermo-dynamical treatment of the QπK phase and a simple combinatorial approach to the hadron-production process are shown to fit available experimental data from AGS, SPS, and RHIC quite well. This approach provides an alternative insight into the actual origin of the observed relative hadronic yields; it is free, to a considerable extent, from well-known puzzles inherent in conventional models that assume an early (high-temperature) chemical freeze-out of hadronic matter. (Within those models, the ideal-gas approximation is in fact employed to describe hadronic matter where hadrons have to be tightly packed and even overlap, which seems doubtful.) Many predictions for the yields of other hadrons that could be observed at these facilities, as well as at the LHC accelerator (under construction in CERN), are made.