QCD phase transition with chiral quarks and physical quark masses

• Published in: Physical review letters Vol. 113; no. 8; p. 082001
• Main Authors: Bhattacharya, Tanmoy, Buchoff, Michael I, Christ, Norman H, Ding, H-T, Gupta, Rajan, Jung, Chulwoo, Karsch, F, Lin, Zhongjie, Mawhinney, R D, McGlynn, Greg, Mukherjee, Swagato, Murphy, David, Petreczky, P, Renfrew, Dwight, Schroeder, Chris, Soltz, R A, Vranas, P M, Yin, Hantao
• Format: Journal Article
• Language: English
• Published: United States 22.08.2014
• ISSN: 1079-7114
• DOI: 10.1103/PhysRevLett.113.082001

We report on the first lattice calculation of the QCD phase transition using chiral fermions with physical 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 is calculated at a single lattice spacing corresponding to a temporal Euclidean extent of N(t) = 8. The disconnected chiral susceptibility, χ(disc) shows a pronounced peak whose position and height depend sensitively on the quark mass. We find no metastability near 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 crossover for m(π) = 135 MeV. The peak location determines a pseudocritical temperature T(c) = 155(1)(8) MeV, in agreement with earlier staggered fermion results. However, the peak height is 50% greater than that suggested by previous staggered results. Chiral SU(2)(L) × SU(2)(R) symmetry is fully restored above 164 MeV, but anomalous U(1)(A) symmetry breaking is nonzero above T(c) and vanishes as T is increased to 196 MeV.