Plasma screening and the critical end point in the QCD phase diagram

TL;DR

This paper uses the Linear Sigma Model with quarks to incorporate plasma screening effects in the QCD phase diagram, suggesting the critical end point may be accessible in low-energy heavy-ion collisions.

Contribution

It introduces plasma screening effects via ring diagrams into the Linear Sigma Model, providing a more comprehensive effective description of the QCD phase diagram.

Findings

The model aligns with LQCD results for the crossover transition.

It predicts the critical end point within the energy range of current experiments.

Long-range correlations are effectively included through plasma screening effects.

Abstract

In heavy-ion collisions, fluctuations of conserved charges are known to be sensitive observables to probe criticality for the QCD phase transition and to locate the position of the putative critical end point (CEP). In this work we seek to show that the Linear Sigma Model with quarks produces an effective description of the QCD phase diagram in which deviations from a Hadron Resonance Gas are due to plasma screening effects, encoded in the contribution of the ring diagrams. Accounting for these, it is possible to include in the description the effect of long-range correlations. To set the model parameters we use LQCD results for the crossover transition at vanishing chemical potential. Finally, studying baryon number fluctuations from the model, we show that the CEP can be located within the HADES and/or the lowest end of the NICA energy domain, $\sqrt{s_{NN}}\sim 2$ GeV.