Subthreshold Anti-Proton K-, K+, and Energetic Pion Production in Relativistic Nucleus-Nucleus Collisions

We present a measurement of subthreshold antiproton, kaon, and energetic pion production at 0{degree} for the reactions {sup 28}Si+{sup 28}Si at 2.0 GeV/nucleon ({ital E}{sub available}/A=0.82 GeV) and 1.65 GeV/nucleon ({ital E}{sub available}/A=0.70 GeV), and for {sup 20}Ne+NaF at 2.0 GeV/nucleon. For a given reaction, the particle yields, plotted as a function of the required excitation energy, exhibit a scaling behavior independent of particle species. Implications for collectivity and a common production mechanism are discussed.