Quantifying corrections to the hadron resonance gas with lattice QCD

TL;DR

This paper uses lattice QCD simulations to quantify deviations from the ideal hadron resonance gas model, providing improved predictions for fluctuations relevant to heavy-ion collision experiments.

Contribution

It introduces a method to determine fugacity expansion coefficients from lattice QCD and applies them to extrapolate fluctuation ratios at finite chemical potentials.

Findings

Reproduces experimental net-proton fluctuation trends

Quantifies corrections to the HRG model

Provides a framework for extrapolating fluctuations

Abstract

The hadron resonance gas (HRG) model and its extensions are often used to describe the hadronic phase of strongly interacting matter. In our work we use lattice-QCD simulations with temporal extents of $N_\tau=8,10$ and $12$ to quantify corrections to the ideal HRG. Firstly, we determine a number of subleading fugacity expansion coefficients of the QCD free energy via a two-dimensional scan on the imaginary baryon number chemical potential ($\mu_B$) - strangeness chemical potential ($\mu_S$) plane. Using the aforementioned coefficients, we also extrapolate ratios of baryon number and strangeness fluctuations and correlations to finite chemical potentials via a truncated fugacity expansion. Our results extrapolated along the crossover line $T_\mathrm{c}(\mu_B)$ at strangeness neutrality are able to reproduce trends of experimental net-proton fluctuations measured by the STAR Collaboration.