PUB - Publikationen an der Universität Bielefeld

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, chi(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(pi) = 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) x 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.