Hagedorn States and Thermalization in Heavy Ion Collisions

TL;DR

This paper explores how Hagedorn states influence thermalization and transport properties in heavy ion collisions, showing they enable rapid chemical equilibrium and reduce viscosity near the QCD critical temperature.

Contribution

It demonstrates that incorporating Hagedorn states explains rapid chemical equilibrium and low viscosity in hadron gases near the QCD phase transition, aligning with lattice results.

Findings

Hagedorn states lower η/s to near the AdS/CFT limit.

Hadrons reach chemical equilibrium almost immediately.

Model aligns with recent lattice QCD results.

Abstract

In recent years, Hagedorn states have been used to explain the equilibrium and transport properties of a hadron gas close to the QCD critical temperature. These massive resonances are shown to lower $\eta/s$ to near the AdS/CFT limit close to the phase transition. A comparison of the Hagedorn model to recent lattice results is made and it is found that the hadrons can reach chemical equilibrium almost immediately, well before the chemical freeze-out temperatures found in thermal fits for a hadron gas without Hagedorn states.