The nature of the finite temperature QCD transition as a function of the quark masses

TL;DR

This paper investigates how the nature of the QCD phase transition at finite temperature depends on quark masses, identifying the critical mass below which a first-order transition occurs.

Contribution

It provides estimates for the critical quark mass separating crossover and first-order regions using improved lattice QCD simulations at different lattice spacings.

Findings

Critical mass estimate for N_T=4: m_0 ≲ 0.07·m_phys

Critical mass estimate for N_T=6: m_0 ≲ 0.12·m_phys

Transition nature depends on quark mass and lattice spacing

Abstract

The finite temperature QCD transition for physical quark masses is a crossover. For smaller quark masses a first-order phase transition is expected. Using Symanzik improved gauge and stout improved fermion action for 2+1 flavour staggered QCD we give estimates/bounds for the phase line separating the first-order region from the crossover one. The calculations are carried out on two different lattice spacings. Our conclusion for the critical mass is $m_0 \lesssim 0.07 \cdot m_{phys}$ for $N_T=4$ and $m_0 \lesssim 0.12 \cdot m_{phys}$ for $N_T=6$ lattices.