Eur. Phys. J. A (2018) 54: 100
https://doi.org/10.1140/epja/i2018-12535-1

Regular Article - Theoretical Physics

Hadron resonance gas model with induced surface tension

¹ Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Metrologichna str. 14b, 03680, Kiev, Ukraine
² CENTRA, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001, Lisboa, Portugal
³ Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183, Linköping, Sweden
⁴ Laboratory for Information Technologies, JINR, Joliot-Curie str. 6, 141980, Dubna, Russia
⁵ National Research Nuclear University “MEPhI” (Moscow Engineering Physics Institute), Kashirskoe Shosse 31, 115409, Moscow, Russia
⁶ Institute for Theoretical Physics, Goethe University, Max-von-Laue-Str. 1, 60438, Frankfurt am Main, Germany
⁷ Institute of Theoretical Physics, University of Wroclaw, pl. M. Borna 9, 50-204, Wroclaw, Poland
⁸ Bogoliubov Laboratory of Theoretical Physics, JINR Dubna, Joliot-Curie str. 6, 141980, Dubna, Russia

^* e-mail: Bugaev@th.physik.uni-frankfurt.de

Received: 10 October 2017
Accepted: 9 May 2018
Published online: 19 June 2018

Abstract

Here we present a generalization of the multicomponent Van der Waals equation of state in the grand canonical ensemble. For the one-component case the third and fourth virial coefficients are calculated analytically. It is shown that the adjustment of a single model parameter allows us to reproduce the third and fourth virial coefficients of the gas of hard spheres with small deviations from their exact values. A thorough comparison of the compressibility factor and speed of sound of this model with the one- and two-component Carnahan-Starling equation of state is made. We show that the model with the induced surface tension can reproduce the results of the Carnahan-Starling equation of state up to the packing fractions 0.2-0.22 at which the Van der Waals equation of state is inapplicable. Using this approach we develop an entirely new hadron resonance gas model and apply it to a description of the hadron yield ratios measured at AGS, SPS, RHIC and ALICE energies of nuclear collisions. We confirm that the strangeness enhancement factor has a peak at low AGS energies and that there is a jump of chemical freeze-out temperature between the two highest AGS energies. Also we argue that the chemical equilibrium of strangeness, i.e. , observed above the center of mass collision energy 8.7 GeV, may be related to a hadronization of quark gluon bags which have a Hagedorn mass spectrum, and, hence, it may be a new signal for the onset of deconfinement.