Interacting hadron resonance gas model in K-matrix formalism

TL;DR

This paper extends the Hadron Resonance Gas model by incorporating interactions via K-matrix formalism, resulting in thermodynamic predictions that align well with lattice QCD data, especially for the interaction measure and conserved charge fluctuations.

Contribution

The work introduces an interacting HRG model using K-matrix formalism, improving agreement with lattice QCD results over the non-interacting model.

Findings

Thermodynamic quantities are larger in the interacting model.

Good agreement with lattice QCD for the equation of state.

Accurate reproduction of second order fluctuations and correlations.

Abstract

An extension of Hadron Resonance Gas (HRG) model is constructed to include interactions using relativistic virial expansion of partition function. The non-interacting part of the expansion contains all the stable baryons and mesons and the interacting part contains all the higher mass resonances which decay into two stable hadrons. The virial coefficients are related to the phase shifts which are calculated using K-matrix formalism in the present work. We have calculated various thermodynamics quantities like pressure, energy density, and entropy density of the system. A comparison of thermodynamic quantities with non interacting HRG model, calculated using the same number of hadrons, shows that the results of above formalism are larger. A good agreement between equation of state calculated in K-matrix formalism and lattice QCD simulations is observed. Specifically the lattice QCD calculated interaction measure is well described in our formalism. We have also calculated second order fluctuations and correlations of conserved charges in K-matrix formalism. We observe a good agreement of second order fluctuations and baryon-strangeness correlation with lattice data below the cross-over temperature.