Critical endline of the finite temperature phase transition for 2+1 flavor QCD around the SU(3)-flavor symmetric point

TL;DR

This study determines the critical endline of the finite temperature phase transition in 2+1 flavor QCD near the SU(3) symmetric point using lattice simulations, confirming the slope and curvature of the endline.

Contribution

It introduces a precise lattice computation of the critical endline in 2+1 flavor QCD around the SU(3) symmetric point, employing reweighting and kurtosis intersection methods.

Findings

The slope of the critical endline is approximately -2.

The second derivative of the endline is positive.

The critical endline is determined at lattice spacing as low as 0.19 fm.

Abstract

We investigate the critical endline of the finite temperature phase transition of QCD around the SU(3)-flavor symmetric point at zero chemical potential. We employ the renormalization-group improved Iwasaki gauge action and non-perturbatively $O(a)$-improved Wilson-clover fermion action. The critical endline is determined by using the intersection point of kurtosis, employing the multi-parameter, multi-ensemble reweighting method to calculate observables off the SU(3)-symmetric point, at the temporal size $N_{\rm T}$=6 and lattice spacing as low as $a \approx 0.19$ fm. We confirm that the slope of the critical endline takes the value of $-2$, and find that the second derivative is positive, at the SU(3)-flavor symmetric point on the Columbia plot parametrized with the strange quark mass $m_s$ and degenerated up-down quark mass $m_{\rm l}$.