Chiral transition and deconfinement in QCD

TL;DR

This paper investigates the nature of the chiral phase transition in two-flavor QCD, providing evidence for a first order transition over second order, using novel finite size scaling analysis techniques.

Contribution

It introduces a new finite size scaling strategy to analyze the order of the chiral phase transition in two-flavor QCD, challenging previous assumptions of second order behavior.

Findings

Evidence against second order O(4) and O(2) universality classes

Substantial evidence for a first order transition

Discussion on scaling violations and future studies

Abstract

The study of QCD with two light dynamical fermions is of fundamental importance to understand the mechanism of color confinement. We present results of a numerical investigation on the order of the chiral phase transition with $N_f = 2$ by use of a novel strategy in finite size scaling analysis. We compare the critical behaviour of the specific heat, of the chiral susceptibility and of the equation of state with the possible critical behaviours. A second order transition in the O(4) and O(2) universality classes are excluded by our data and substantial evidence emerges for a first order transition. Like in most of previous works we have used the standard staggered action with $L_t = 4$: possible scaling violations and the need for further studies are discussed.