Finite temperature QCD phase transition and its scaling window from Wilson twisted mass fermions

A.Yu Kotov,M.P Lombardo,A Trunin,A Rothkopf,L Tolos,D Röhrich,N Brambilla,K Tywoniuk,A Kurkela,A Tranberg,J.O Andersen

doi:10.1051/epjconf/202225805012

Abstract

We study the properties of finite temperature QCD using lattice simulations with Nf = 2 + 1 + 1 Wilson twisted mass fermions for pion masses from physical up to heavy quark regime. In particular, we investigate the scaling properties of the chiral phase transition close to the chiral limit. We found compatibility with O(4) universality class for pion masses up to physical and in the temperature range [120 : 300] MeV. We also discuss other alternatives, including mean field behaviour or Z2 scaling. We provide an estimation of the critical temperature in the chiral limit, T0 = 134−4+6 MeV, which is stable against various scaling scenarios.

Highlights

The phase diagram of Quantum Chromodynamics (QCD) has been actively investigated for many years
It is conceivable that the two phenomena are not related, and there are suggestions of a possible large splitting between deconfinement and chiral symmetry restoration phase transitions, including specific quarkyonic phase [1] at high density or a possible onset of deconfinement in QCD at temperatures higher than chiral phase transition [2, 3]
In particular we look at the onset of the scaling window, related to the behaviour of QCD in the chiral limit m ! 0

Summary

Introduction

The phase diagram of Quantum Chromodynamics (QCD) has been actively investigated for many years. As it is well known, chiral symmetry is well defined only for massless quarks, and confinement can be described as a phase transition with an associated order parameter only in pure gauge systems, or, equivalently, in the infinite quark mass limit, where quarks decouple. The pseudo-critical temperature extracted from the inflection point of the new order parameter corresponds to x = 0.55(1), which is lower than the pseudocritical temperature determined by the inflection point of the chiral condensate, x = 0.74(4). We extract the pseudo-critical temperature from the inflection point of the chiral condensate and new order parameter hi and from the peak of susceptibility. Of T0, while the critical temperature obtained by extrapolation of the data for the chiral condensate is slightly higher It might indicate possible larger violations of scaling in the chiral condensate.

Behaviour of hi3

Z2 scaling

Conclusions