Mass-identified Particle Production in Proton-Antiproton Collisions at Sqrt S =300, 540, 1000, and 1800 GeV.

The yields and average transverse momenta of pions, kaons, and antiprotons produced at the Fermilab ppBAR collider at square-root s = 300, 540, 1000, and 1800 GeV are presented and compared with data from the energies reached at the CERN collider. We also present data on the dependence of average transverse momentum [p(t)] and particle ratios as a function of charged particle density dN(c)/deta; data for particle densities as high as six times the average value, corresponding to a Bjorken energy density 6 GeV/fm3, are reported. These data are relevant to the search for quark-gluon phase of QCD.