TY  - JOUR
A1  - Zschiesche, Detlef
A1  - Schramm, Stefan
A1  - Schaffner-Bielich, Jürgen
A1  - Stöcker, Horst
A1  - Greiner, Walter
T1  - Particle ratios at RHIC: Effective hadron masses and chemical freeze-out
T2  - Physics Letters B
N2  - The measured particle ratios in central heavy-ion collisions at RHIC-BNL are investigated within a chemical and thermal equilibrium chiral SU(3) σ–ω approach. The commonly adopted noninteracting gas calculations yield temperatures close to or above the critical temperature for the chiral phase transition, but without taking into account any interactions. Contrary, the chiral SU(3) model predicts temperature and density dependent effective hadron masses and effective chemical potentials in the medium and a transition to a chirally restored phase at high temperatures or chemical potentials. Three different parametrizations of the model, which show different types of phase transition behaviour, are investigated. We show that if a chiral phase transition occured in those collisions, “freezing” of the relative hadron abundances in the symmetric phase is excluded by the data. Therefore, either very rapid chemical equilibration must occur in the broken phase, or the measured hadron ratios are the outcome of the dynamical symmetry breaking. Furthermore, the extracted chemical freeze-out parameters differ considerably from those obtained in simple noninteracting gas calculations. In particular, the three models yield up to 35 MeV lower temperatures than the free gas approximation. The in-medium masses turn out to differ up to 150 MeV from their vacuum values.
Y1  - 2002
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/76020
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-760201
SN  - 0370-2693
VL  - 547
IS  - 1-2
SP  - 7
EP  - 14
PB  - North-Holland Publ.
CY  - Amsterdam [u.a.]
ER  -