Topology, fermionic zero modes, and flavor singlet correlators in finite temperature QCD

We compute the screening correlators in the σ and η^' flavor singlet channels in finite temperature QCD with 2 light quark flavors. Together with the correlators in the →π and →δ channels, these are used to discuss several issues related to symmetry restoration and the nature of the QCD phase transition. Our calculations span a range of temperature extending from approximately 125 MeV to 170 MeV and are carried out in the context of a staggered fermion formulation on a 16³×8 lattice. In addition to the computation at a fixed quark mass (amq=0.00625), we discuss the issue of the chiral limit. After careful consideration of the zero-mode shift lattice artifact, we present rather strong (topological) arguments in favor of the non-restoration of UA(1) at Tc.