# Chiral phase transition in (2 + 1)-flavor QCD

## TL;DR

This study uses lattice QCD simulations with improved staggered quarks to estimate the chiral phase transition temperature in (2+1)-flavor QCD, finding no evidence of a first-order transition and providing a precise temperature estimate.

## Contribution

The paper introduces new estimators for the chiral transition temperature and performs extensive simulations to analyze its dependence on quark mass and volume.

## Key findings

- No evidence for a first-order phase transition in the studied quark mass range.
- Estimated chiral transition temperature is approximately 132 MeV.
- Simulations cover multiple lattice spacings and quark masses, ensuring robust results.

## Abstract

The chiral phase transition temperature $T_{c}^{0}$ is a fundamental quantity of QCD. To determine this quantity we have performed simulations of (2 + 1)-flavor QCD using the Highly Improved Staggered Quarks (HISQ/tree) action on $N_{\tau}=6, 8$ and 12 lattices with aspect ratios $N_{\sigma}/N_{\tau}$ ranging from 4 to 8. In our simulations the strange quark mass is fixed to its physical value $m_{s}^{\rm{phy}}$, and the values of two degenerate light quark masses $m_{l}$ are varied from $m_{s}^{\rm{phy}}/20$ to $m_{s}^{\rm{phy}}/160$ which correspond to a Goldstone pion mass $m_{\pi}$ ranging from 160 MeV to 55 MeV in the continuum limit. By investigating the light quark mass dependence and the volume dependence of various chiral observables, e.g. chiral susceptibilities and Binder cumulants, no evidence for a first order phase transition in our current quark mass window is found. Two estimators $T_{60}$ and $T_{\delta}$ are proposed to extract the chiral phase transition temperature $T_{c}^{0}$ in the chiral and continuum limit and our current estimate for $T_{c}^{0}$ is $132_{-6}^{+3}$ MeV.