Is there still any Tc mystery in lattice QCD? Results with physical masses in the continuum limit III

TL;DR

This paper investigates the QCD cross-over transition temperatures using refined lattice simulations with physical quark masses, confirming previous results and explaining discrepancies with other studies through spectrum distortions.

Contribution

It extends previous lattice QCD studies to finer lattices with physical masses and clarifies the discrepancy with hotQCD results via spectrum analysis.

Findings

Results agree with earlier studies on transition temperatures.

Discrepancies with hotQCD are explained by lattice artifacts and heavier quark masses.

Analytic models reproduce results when using physical spectra.

Abstract

The present paper concludes our investigations on the QCD cross-over transition temperatures with 2+1 staggered flavours and one-link stout improvement. We extend our previous two studies [Phys. Lett. B643 (2006) 46, JHEP 0906:088 (2009)] by choosing even finer lattices ($N_t$=16) and we work again with physical quark masses. The new results on this broad cross-over are in complete agreement with our earlier ones. We compare our findings with the published results of the hotQCD collaboration. All these results are confronted with the predictions of the Hadron Resonance Gas model and Chiral Perturbation Theory for temperatures below the transition region. Our results can be reproduced by using the physical spectrum in these analytic calculations. The findings of the hotQCD collaboration can be recovered by using a distorted spectrum which takes into account lattice discretization artifacts and heavier than physical quark masses. This analysis provides a simple explanation for the observed discrepancy in the transition temperatures between our and the hotQCD collaborations.