Measuring the hadronic spectrum of the quark plasma

In an effort to characterize the large-scale structure and composition of the QCD plasma at zero baryon-number density in the vicinity of the high-temperature phase transition, we have carried out a numerical simulation in SU(3) lattice gauge theory with four flavors of low-mass staggered fermions on a 6×${10}^3$ lattice. A small data sample was also collected on 6×${10}^2$×20 lattices. The simulation uses the Illinois hybrid microcanonical algorithm, adapted for measurements of hadronic screening lengths. Measurements were carried out at three values of the gauge coupling β and at three values each of the bare quark mass. The principal quantities measured are the static screening masses in several color-singlet channels with quark valence qq¯ and qqq. Clear evidence for a hadronic screening spectrum is found, suggesting the presence of hadronic plasma modes. The spectral multiplets, extrapolated to zero quark mass, are consistent with a restoration of the SU(N)×SU(N) chiral symmetry.