QCD transition at the physical point, and its scaling window from twisted mass Wilson fermions

We study the scaling properties of the finite temperature QCD phase transition, for light quark masses ranging from the heavy quark regime to their physical values. The lattice results are obtained in the fixed scale approach from simulations of N-f = 2 + 1 + 1 flavours of Wilson fermions at maximal twist. We identify an order parameter free from the linear contributions in mass due to additive renormalization and regular terms in the Equation of State, which proves useful for the assessment of the hypothesized universal behaviour. We find compatibility with the 3D O (4) universality class for the physical pion mass and temperatures 120 MeV less than or similar to T less than or similar to 300 MeV. We discuss violation of scaling at larger masses and a possible cross-over to mean field behaviour. The chiral extrapolation T-0 = 134(-4)(+6) MeV of the pseudocritical temperature is robust against predictions of different universality classes and consistent with its estimate from the O (4) Equation of State for the physical pion mass. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

In this study, the scaling properties of the finite temperature QCD phase transition were investigated for different light quark masses using simulations of Wilson fermions. An order parameter free from linear contributions in mass was identified, which proved useful for assessing universal behavior. The results were found to be compatible with the 3D O (4) universality class for the physical pion mass and temperatures within the range of 120 MeV to 300 MeV.