Abstract
Using an advanced version of the hadron resonance gas model we have found several remarkable irregularities at chemical freeze-out. The most prominent of them are two sets of highly correlated quasi-plateaus in the collision energy dependence of the entropy per baryon, total pion number per baryon, and thermal pion number per baryon which we found at center of mass energies 3.6-4.9 GeV and 7.6-10 GeV. The low energy set of quasi-plateaus was predicted a long time ago. On the basis of the generalized shock-adiabat model we demonstrate that the low energy correlated quasi-plateaus give evidence for the anomalous thermodynamic properties of the mixed phase at its boundary to the quark-gluon plasma. The question is whether the high energy correlated quasi-plateaus are also related to some kind of mixed phase. In order to answer this question we employ the results of a systematic meta-analysis of the quality of data description of 10 existing event generators of nucleus-nucleus collisions in the range of center of mass collision energies from 3.1 GeV to 17.3 GeV. These generators are divided into two groups: the first group includes the generators which account for the quark-gluon plasma formation during nuclear collisions, while the second group includes the generators which do not assume the quark-gluon plasma formation in such collisions. Comparing the quality of data description of more than a hundred of different data sets of strange hadrons by these two groups of generators, we find two regions of the equal quality of data description which are located at the center of mass collision energies 4.3-4.9 GeV and 10.-13.5 GeV. These two regions of equal quality of data description we interpret as regions of the hadron-quark-gluon mixed phase formation.
Highlights
The hadron resonance gas model (HRGM) [1] is traditionally used to extract the parameters of chemical freeze-out (CFO) from the measured hadronic yields
The most prominent of them are two sets of highly correlated quasi-plateaus in the collision energy dependence of the entropy per baryon, total pion number per baryon, and thermal pion number per baryon which we found at center of mass energies 3.6-4.9 GeV and 7.6-10 GeV
On the basis of the generalized shockadiabat model we demonstrate that the low energy correlated quasi-plateaus give evidence for the anomalous thermodynamic properties of the mixed phase at its boundary to the quark-gluon plasma
Summary
The hadron resonance gas model (HRGM) [1] is traditionally used to extract the parameters of chemical freeze-out (CFO) from the measured hadronic yields. The achieved high quality χ2/do f 0.95 [5, 6] of data description of 111 independent hadron yield r√atios measured at midrapidity in central nucleus-nucleus collisions at the center of mass energies sNN = 2.7, 3.1, 3.6, 4.3, 4.9, 6.3, 7.6, 8.8, 9.2, 12.3, 17.3, 62.4, 130, 200 GeV proves that the multicomponent version of HRGM is a precise and a sensitive tool of heavy ion collision phenomenology. In order to correctly interpret the high energy quasi-plateaus here we use the results of meta-analysis [12] of the quality of data description (QDD) of 10 existing event generators of nucleus-nucleus collisions along with the thorough analysis of irregularities in the existing experimental hadron yield ratios.
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