Ratio of the average number of π- mesons to the average number of interacting protons in central nucleus-nucleus collisions

The ratio R = / of the average number of negative pions to the average number of interacting protons has been measured for inelastic collisions of 12C nuclei with C, Ne, Si, and Zr nuclei, and of 20Ne nuclei with Ne and Zr nuclei and for central collisions of 12C nuclei with Ne, Cu, and Zr nuclei, of 16O nuclei with Ne nuclei, and of 20Ne nuclei with Ne and Zr nuclei at an incident kinetic energy of 3.6 GeV/nucleon. It is shown that R remains roughly constant throughout the investigated range of mass numbers of the interacting nuclei, is the same for inelastic and central collisions, and is independent of the criteria used to select central collisions. The results, together with data from other experiments at lower energies (0.5< or =E/sub kin/< or =2.1 GeV/nucleon), show that R depends linearly on the energy