The transition temperature in QCD

TL;DR

This paper calculates the QCD transition temperature using lattice simulations with improved staggered fermions, extrapolating to physical quark masses and the continuum limit, resulting in a precise estimate of T_c around 192 MeV.

Contribution

It provides a detailed lattice QCD determination of the transition temperature with improved methods and extrapolations to physical quark masses and continuum limit, refining previous estimates.

Findings

Transition temperature T_c ≈ 192 MeV at physical quark masses.

Transition temperature in the chiral limit is about 3% smaller.

Universal scaling behavior observed in thermodynamic quantities.

Abstract

We present a detailed calculation of the transition temperature in QCD with two light and one heavier (strange) quark mass on lattices with temporal extent N_t =4 and 6. Calculations with improved staggered fermions have been performed for various light to strange quark mass ratios in the range, 0.05 <= m_l/m_s <= 0.5, and with a strange quark mass fixed close to its physical value. From a combined extrapolation to the chiral (m_l -> 0) and continuum (aT = 1/N_t -> 0) limits we find for the transition temperature at the physical point T_c r_0 = 0.457(7) where the scale is set by the Sommer-scale parameter r_0 defined as the distance in the static quark potential at which the slope takes on the value, (dV_qq(r)/dr)_r=r_0 = 1.65/r_0^2. Using the currently best known value for r_0 this translates to a transition temperature T_c = 192(7)(4)MeV. The transition temperature in the chiral limit is about 3% smaller. We discuss current ambiguities in the determination of T_c in physical units and also comment on the universal scaling behavior of thermodynamic quantities in the chiral limit.