Revealing the Signal of QCD Phase Transition in Heavy-Ion Collisions

TL;DR

This paper introduces a new method to analyze fluctuations in heavy-ion collisions to detect signals of the QCD phase transition, including the critical end-point and first order phase transition, emphasizing the need for higher precision data.

Contribution

A novel approach to construct the Landau thermodynamic potential from experimental fluctuations to identify QCD phase transition signals.

Findings

Most collision energies show no FOPT signal.

Data at 7.7 GeV suggests possible FOPT signal, but uncertainties remain.

Higher order fluctuations are needed for confirmation.

Abstract

We propose a novel method to construct the Landau thermodynamic potential directly from the fluctuations measured in heavy-ion collisions. The potential is capable of revealing the signal of the critical end-point (CEP) and the first order phase transition (FOPT) of QCD in the system even away from the phase transition region. With the available experimental data, we show that the criterion of the FOPT is negative for most of the collision energies which indicates no signal of FOPT. The data at $\sqrt{s_\mathrm{NN}}=7.7$ GeV with 0-5% centrality shows a different behavior and the mean value of the data satisfies the criterion. However, the uncertainty is still too large to make a certain conclusion. The higher order fluctuations are also required for confirming the signal. We emphasize therefore that new measurements with higher precision for the $C_{1,...,6}$ within 0-5% centrality in the vicinity of $\sqrt{s_\mathrm{NN}}=7.7$ GeV are in demand which may finally reveal the signal of QCD phase transition.