2014/02/21 by Tanmoy Bhattacharya, Michael I. Buchoff, Norman H. Christ +14 · 2 citations
Physics and Astronomy · #hep-lat
paper · pdf · doi:10.1103/physrevlett.113.082001
published as Phys. Rev. Lett. 113, 082001 (2014) · 6 pages and 4 figures
arxiv created 2014/02/21 · arxiv updated 2014/08/27
We report on the first lattice calculation of the QCD phase transition using chiral fermions at physical values of the quark masses. This calculation uses 2+1 quark flavors, spatial volumes between (4 fm)3 and (11 fm)3 and temperatures between 139 and 196 MeV . Each temperature was calculated using a single lattice spacing corresponding to a temporal Euclidean extent of Nt=8. The disconnected chiral susceptibility, χ\rm disc shows a pronounced peak whose position and height depend sensitively on the quark mass. We find no metastability in the region of the peak and a peak height which does not change when a 5 fm spatial extent is increased to 10 fm. Each result is strong evidence that the QCD ``phase transition'' is not first order but a continuous cross-over for mπ=135 MeV. The peak location determines a pseudo-critical temperature Tc = 155(1)(8) MeV. Chiral SU(2)L× SU(2)R symmetry is fully restored above 164 MeV, but anomalous U(1)A symmetry breaking is non-zero above Tc and vanishes as T is increased to 196 MeV.