The QCD transition temperature: results with physical masses in the continuum limit II.

TL;DR

This work extends the determination of the QCD crossover temperature $T_c$ by simulating with physical quark masses and finer lattice spacings, and by validating scale setting against multiple hadronic inputs. It confirms that zero-temperature observables align with experimental values and that the continuum-limit results for $T_c$ are independent of the particular quantity used to set the scale within about $2\%$. Finite-temperature results show that different observables yield different $T_c$ values in a crossover, giving a range of roughly $146$–$170$ MeV, and reveal a substantial ~35 MeV discrepancy with the hotQCD results that persists across several renormalized observables. The study highlights remaining tensions between lattice groups and emphasizes the need for cross-checks using different fermion discretizations (e.g., Wilson-type) to solidify the thermodynamics of QCD in the continuum limit.

Abstract

We extend our previous study [Phys. Lett. B643 (2006) 46] of the cross-over temperatures (T_c) of QCD. We improve our zero temperature analysis by using physical quark masses and finer lattices. In addition to the kaon decay constant used for scale setting we determine four quantities (masses of the Ωbaryon, K^*(892) and φ(1020) mesons and the pion decay constant) which are found to agree with experiment. This implies that --independently of which of these quantities is used to set the overall scale-- the same results are obtained within a few percent. At finite temperature we use finer lattices down to a <= 0.1 fm (N_t=12 and N_t=16 at one point). Our new results confirm completely our previous findings. We compare the results with those of the 'hotQCD' collaboration.