Measuring the hadronic spectrum of the quark plasma

In an effort to characterize the large-scale structure and composition of the Q C D 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 x 103 lattice. A small data sample was also collected on 6 x 102 X 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 B 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) X SU (N) chiral symmetry.