Critical line of 2+1 flavor QCD: Toward the continuum limit

TL;DR

This study calculates the continuum limit of the curvature of the QCD pseudocritical line with 2+1 flavors, using lattice simulations at imaginary chemical potential, and compares the results with experimental data and other lattice results.

Contribution

It provides a new estimate of the continuum curvature of the QCD pseudocritical line at zero baryon density using improved lattice techniques.

Findings

Estimated continuum curvature $oxed{ ext{0.020(4)}}$ at zero baryon density.

Results are consistent with recent lattice and experimental data.

Performed extrapolation to the continuum limit up to $L_t=12$.

Abstract

We determine the continuum limit of the curvature of the pseudocritical line of QCD with $n_f$=2+1 staggered fermions at nonzero temperature and quark density. We perform Monte Carlo simulations at imaginary baryon chemical potentials, adopting the HISQ/tree action discretization, as implemented in the code by the MILC collaboration. Couplings are adjusted so as to move on a line of constant physics, as determined in Ref.~\cite{Bazavov:2011nk}, with the strange quark mass $m_s$ fixed at its physical value and a light-to-strange mass ratio $m_l/m_s=1/20$. The chemical potential is set at the same value for the three quark species, $\mu_l=\mu_s\equiv \mu$. We attempt an extrapolation to the continuum using the results on lattices with temporal size up to $L_t=12$. Our estimate for the continuum value of the curvature $\kappa$ at zero baryon density, $\kappa=0.020(4)$, is compared with recent lattice results and with experimental determinations of the freeze-out curve.