Hagedorn States and Thermalization

TL;DR

This paper explores how Hagedorn states influence thermalization and chemical equilibrium in hadron gases near the critical temperature, showing they can rapidly achieve equilibrium and affect observable particle ratios.

Contribution

It demonstrates that Hagedorn states enable rapid chemical equilibration and significantly impact hadron gas properties near the phase transition.

Findings

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

Hadrons reach chemical equilibrium almost immediately with Hagedorn states.

Hagedorn states influence the K+/π+ ratio observed at various colliders.

Abstract

In recent years Hagedorn states have been used to explain the physics close to the critical temperature within a hadron gas. Because of their large decay widths these massive resonances lower $\eta/s$ to near the AdS/CFT limit within the hadron gas phase. A comparison of the Hagedorn model to recent lattice results is made and it is found that for both Tc =176 MeV and Tc=196 MeV, 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. In this paper we also observe the effects of Hagedorn States on the $K^+/\pi^+$ horn seen at AGS, SPS, and RHIC.