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Mean-field approach in the multi-component gas of interacting particles applied to relativistic heavy-ion collisions

Generalized mean-field approach for thermodynamic description of relativistic single- and multi-component gas in the grand canonical ensemble is formulated. In the framework of the proposed approach different phenomenological excluded-volume procedures are presented and compared to the existing ones. The mean-field approach is then used to effectively include hard-core repulsion in hadron-resonance gas model for description of chemical freeze-out in heavy-ion collisions. We calculate the collision energy dependence of several quantities for different values of hard-core hadron radius and for different excluded-volume procedures such as van der Waals and Carnahan-Starling models. It is shown that a choice of the excluded-volume model becomes important for large particle densities. For large enough values of hadron radii ($r\gtrsim0.9$ fm) there can be a sizable difference between different excluded-volume procedures used to describe the chemical freeze-out in heavy-ion collisions. At the same time, for the smaller and more commonly used values of hard-core hadron radii ($r\lesssim0.5$ fm), the precision of the van der Waals excluded-volume procedure is shown to be sufficient.