MEASUREMENTS OF POSITRONS FROM PAIR PRODUCTION IN COULOMB COLLISIONS OF 33-TEV LEAD IONS WITH FIXED TARGETS

Free positrons from electron-positron pairs produced by 33-TeV Pb82+ i ons in Coulomb collisions with targets of carbon [(CH)(x)], aluminum, palladium, and gold have been measured to determine cross sections and momentum distributions. Upper limits have been established for contri butions from multiple pair formation. Comparison with similar data tak en for 6.4-TeV S16+ ions shows that cross sections scale as the produc t of the squares of the projectile and target nuclear charges. Positro n momentum distributions for S16+ and Pb82+ ions on all targets are ob served to be similar, but indicate a tendency for higher-energy positr on emission for the Pb82+ projectiles. [S1050-2947(97)01711-3].