Thermal model analysis of particle ratios in Ni+Ni experiments using exact strangeness conservation

Abstract

The production of hadrons in Ni-Ni at the GSI laboratory is considered in a hadronic gas model with chemical equilibrium. Special attention is given to the abundance of strange particles which are treated using the exact conservation of strangeness. It is found that all the data can be described using a temperature T ϭ70Ϯ10 MeV and a baryon chemical potential B ϭ720Ϯ30 MeV. ͓S0556-2813͑98͒01706-3͔

Hadron production in central nucleus–nucleus collisions at chemical freeze-out

“…It is established that γ S ≃ 1 for central collisions at RHIC [8,9]. At the lower end of the energy range, namely at SIS energies (up to 2 AGeV), there are indications [3] that γ S is not needed either. As we investigate central Au-Au or Pb-Pb collisions we prefer to stay within the thermodynamically well defined equilibrium model.…”

“…5) one cannot constrain the canonical volume parameter. As a consequence, and since the canonical volume dependence is a rather small effect, we have chosen the value V C =1000 fm 3 . We mention that µ b is unaffected by the canonical volume choice.…”

“…The thermal model was initially used for the AGS and SPS data [2] and was subsequently employed to describe data at SIS [3,4], SPS [5] and more recently at RHIC [6,7,8,9]. An analysis of the energy dependence of the thermal parameters extracted from fits of the experimental data, temperature (T ) and baryo-chemical potential (µ b ), established the "line of chemical freeze-out" [10].…”

Statistical ensembles with finite bath: A description for an event generator

“…Let us consider a static and neutral system with fourvelocity u µ = (1, 0, 0, 0), chemical potentials µ j = (0, 0, 0), local temperature T = β −1 = 0.160 GeV, and volume V 1 = 2000 fm 3 . This is a system large enough 3 to use the large volume approximation worked out in Sec.…”

“…The statistical hadronization model, first introduced by Fermi [1] and Hagedorn [2], has been remarkably successful in the description of experimentally measured average hadron production yields in heavy-ion collisions ranging from the GSI Schwerionen Synchrotron (SIS) [3] and BNL Alternating Gradient Synchrotron (AGS) [4] over CERN Super Proton Synchrotron (SPS) [5] to BNL Relativistic Heavy Ion Collider (RHIC) [6] energies. Over time this has led to the establishment of the "chemical freeze-out line" [7], which is now a vital part of our understanding of the phase diagram of strongly interacting matter.…”