# Quark Matter 2014 - XXIV International Conference on Ultrarelativistic Nucleus-Nucleus Collisions

19-24 May 2014
Europe/Zurich timezone

## Chemical Freeze-out Irregularities and Quark Gluon Bags Formation

20 May 2014, 16:30
2h

Board: J-03

### Speakers

Mr Dmytro Oliinychenko (Frankfurt Institute for Advanced Studies, Frankfurt, Germany) Prof. Kyrill Bugaev (Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine)

### Description

We made a thorough analysis of the hadron resonance gas model for the Breit-Wigner and for the Gauss resonance width parameterizations [1]. The latter model allows us to treat the usual hadrons and the quark gluon bags on the same footing and to study the stability of the results obtained within different formulations of the hadron resonance gas model. Three versions of this model are fitted to reproduce 111 independent hadronic multiplicity ratios measured for 14 values of the center of mass collision energies in the interval $\sqrt{s_{NN}} =$ 2.7--200 GeV. We found that in a narrow range of collision energy $\sqrt{s_{NN}} =$ 4.3--4.9 GeV there exist the peculiar irregularities in various thermodynamic quantities calculated at chemical freeze-out. The most remarkable irregularity is an unprecedented jump of the number of effective degrees of freedom observed in this narrow energy range which is seen in all realistic versions of the hadron resonance gas model. Thus, the ratio of the freeze-out entropy density to the cube of its temperature and the ratio of the freeze-out pressure to its temperature to the fourth are, respectively, increased in 1.67 and 1.5 times, while the center of mass collision energy changes on about 14 \% (see figure below). We are arguing that these irregularities evidence for the formation of quark gluon bags. To understand such irregularities we study the apparent width of wide hadronic resonances and quark gluon bags in a thermal medium. We discuss two new effects generated for the wide resonances and quark gluon bags by a thermal medium near the threshold of decay: their thermal enhancement and their thermal sharpening. We argue that the most optimistic chance to experimentally find the quark gluon bags may be related to their sharpening and enhancement in a thermal medium. In this case the wide quark gluon bags may appear directly or in decays as narrow resonances which are absent in the tables of elementary particles and which have the width of about 50-150 MeV and the mass of about or above 2.5 GeV. 1. K. A. Bugaev, A.I. Ivanytskyi, D. R. Oliinychenko, E. G. Nikonov, V. V. Sagun and G. M. Zinovjev, arXiv:1312.4367 [hep-ph].

### Primary author

Prof. Kyrill Bugaev (Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine)

### Co-authors

Mr Aleksei Ivanytskyi (Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine) Mr Dmytro Oliinychenko (Frankfurt Institute for Advanced Studies, Frankfurt, Germany) Prof. Edward Nikonov (Laboratory for Information Technologies, JINR, Dubna, Russia) Prof. Gennadyi Zinovjev (Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine) Ms Violetta Sagun (Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine)

 Slides