Particle Ratios as a Probe of the QCD Critical Temperature

TL;DR

This paper demonstrates how particle ratios in heavy-ion collisions can be used to estimate the QCD critical temperature by incorporating Hagedorn resonances into statistical models, improving fit accuracy.

Contribution

It introduces the inclusion of Hagedorn states in thermal models to better determine the QCD critical temperature from experimental data.

Findings

Best fit at T_c ≈ 176 MeV for RHIC Au+Au collisions

Chemical freeze-out temperature around 172.6 MeV

Baryon chemical potential approximately 39.7 MeV

Abstract

We show how the measured particle ratios can be used to provide non-trivial information about the critical temperature of the QCD phase transition. This is obtained by including the effects of highly massive Hagedorn resonances on statistical models, which are used to describe hadronic yields. The inclusion of Hagedorn states creates a dependence of the thermal fits on the Hagedorn temperature, $T_H$, which is assumed to be equal to $T_c$, and leads to an overall improvement of thermal fits. We find that for Au+Au collisions at RHIC at $\sqrt{s_{NN}}=200$ GeV the best square fit measure, $\chi^2$, occurs at $T_c \sim 176$ MeV and produces a chemical freeze-out temperature of 172.6 MeV and a baryon chemical potential of 39.7 MeV.