Hadron Resonance Gas (HRG) Module
The HRG (Hadron Resonance Gas) module of the NSF-funded MUSES project provides methods for calculating the equation of state (EoS) of strongly interacting hadronic matter at zero and finite temperature \(T\), baryon chemical potential \(\mu_B\), strangeness chemical potential \(\mu_S\), and charge chemical potential \(\mu_Q\). It can be used to compute the EoS of an ideal hadron resonance gas (IHRG) as well as a quantum van der Waals (QvdW) HRG, which includes mean-field interactions between hadrons.
The module relies on the Thermal-FIST package (Thermal, Fast and Interactive Statistical Toolkit) version 1.6, with its C++ source code (GPLv3) available on GitHub.
- It can be used to compute the HRG EoS over the range:
Temperature: \(0 < T < 300\) MeV
Chemical potentials: Accessible range of chemical potentials, \(\mu = \sqrt{\mu_B^2 + \mu_Q^2 + \mu_S^2}\), typically extending from 0 to 1000 MeV. Calculations should be performed only outside the condensation region, defined by the conditions: \(\mu_Q < m_\pi\), \(\mu_S < m_{K^0}\), and \((\mu_S + \mu_Q) < m_{K^\pm}\); however, the use of interacting pions through an effective mass model allows for calculations in the pion condensation region, currently restricted to \(\mu_Q < 2 \times m_\pi\).