PUB - Publikationen an der Universität Bielefeld

While the Polyakov loop is an order parameter of the deconfinement transition in the heavy quark mass regime of QCD, its sensitivity to the deconfinement of light, dynamical quarks in QCD are not apparent. On the other hand, the quark mass dependence of the Polyakov loop is sensitive to the appearance of a chiral phase transition. Using lattice QCD calculations in the staggered fermion discretization scheme at finite values of the lattice spacing, aT=1/8, we show here, for the first time, that the Polyakov loop expectation value, and the heavy quark free energy extracted from it, behaves like an energylike observable in the vicinity of the chiral phase transition temperature Tc. Consistent with scaling behavior of energylike observables in the 3d, O(2) universality class, the quark mass derivatives diverge in the chiral limit at Tc while the temperature derivatives stay finite. The latter will develop a characteristic spike at Tc. This, however, may be resolved only in calculations with quark masses being 2 orders of magnitude smaller than those currently accessible in lattice QCD calculations.