Description of hot and dense hadron-gas properties in a new excluded-volume model

Abstract

A new equation of state for a hot and dense hadron gas (HG) is obtained where the finite hard-core size of baryons has been incorporated in a thermodynamically consistent formulation of excluded volume correction. Our model differs from other existing approaches on the following points. We assign a hard-core volume only to each baryon and mesons though possess a small volume but they can fuse and interpenetrate into one another. Use of the full quantum statistics is made in obtaining the grand canonical partition function where excluded-volume correction has been incorporated by explicitly integrating over volume. We thus find that the new model works even for the cases of extreme temperatures and/or densities where most of other approaches fail.The model does not violate causality even at extreme densities. The temperature and density dependence of various thermodynamical quantities, e.g. pressure, baryon density, entropy and energy density compare well with the results of other microscopic HG models. After suitable parametrization of the centre-of-mass energy in terms of temperature and baryon chemical potential, we explore some new freeze-out criteria which exhibit full independence of the collision energy and of the structures of the colliding nuclei. We further demonstrate the suitability of our model in explaining various experimental results of the multiplicity-ratios of various particles and their antiparticles. Finally, we use our excluded-volume model to obtain the transport behaviour of the hot and/or dense HG such as shear viscosity to entropy ratio, speed of sound etc. and compare the results with earlier calculations.

Bulk and shear viscosities of hot and dense hadron gas

“…This in turn makes a larger value for the ratio η s We also looked into the behavior of η s at low temperatures as a function of µ where it shows a valley structure which is plotted in Fig.7. Such an observation was also made in Ref.s [24,25,49]. The existence of a minimum of η/s was interpreted in these references indicative of a liquid gas phase transition.…”

Transverse momentum distribution and elliptic flow of charged hadrons in $$U+U$$ U + U collisions at $$\sqrt{s_{NN}}=193$$ s NN = 193 GeV using HYDJET++

“…After that we have to modify the freeze-out hypersurface to properly include the effect of nuclear deformation via change in number of participants. There are various ways to generate the initial conditions for chemical and thermal freeze-out hypersurface [44][45][46][47]. However we first want to start here with the hydrodynamic evolution of this freeze-out hypersurface i.e., the hydrodynamic evolution laws for QCD medium.…”

“…Now to calculate the initial temperature in our calculations we have used a parameterization based on ideal thermal gas approximation [46,48] where…”

Limiting fragmentation in a thermal model with flow

“…This model has been successful in explaining various aspects of particle production in heavy-ion collisions, likeparticle spectra, ratios etc. at RHIC and LHC energies [55]. We take the hadrons and their resonances having masses up to 2 GeV.…”

“…We use the chemical freeze-out criteria proposed in our model [55] to obtain temperature (T) and baryon chemical potential (µ B ) at various center-of-mass energies. The paper is organized as follows: we first discuss the formulation of our model for HG and then we discuss its applicability in describing the rapidity distribution.…”