Curvature of the pseudocritical line in QCD: Taylor expansion matches analytic continuation

TL;DR

This paper accurately determines the curvature of the QCD pseudo-critical line using Taylor expansion and confirms it with analytic continuation, resolving previous discrepancies between methods.

Contribution

It provides a precise continuum-extrapolated value of the QCD pseudo-critical line curvature using Taylor expansion, matching results from analytic continuation with improved discretization.

Findings

Continuum extrapolated curvature: 0.0145(25)

Agreement between Taylor expansion and analytic continuation

Elimination of previous methodological tension

Abstract

We determine the curvature of the pseudo-critical line of $N_f = 2 + 1$ QCD with physical quark masses via Taylor expansion in the quark chemical potentials. We adopt a discretization based on stout improved staggered fermions and the tree level Symanzik gauge action; the location of the pseudocritical temperature is based on chiral symmetry restoration. Simulations are performed on lattices with different temporal extent ($N_t = 6, 8, 10$), leading to a continuum extrapolated curvature $\kappa = 0.0145(25)$, which is in very good agreement with the continuum extrapolation obtained via analytic continuation and the same discretization, $\kappa = 0.0135(20)$. This result eliminates the possible tension emerging when comparing analytic continuation with earlier results obtained via Taylor expansion.