Number 168 (Story #1), March 10, 1994 by Phillip F. Schewe and Ben Stein HIGH ENERGY SULPHUR-SULPHUR COLLISIONS at the CERN SPS accelerator exhibit a greater "stopping power" or "stickiness" than proton-proton collisions. That is, when two heavy nuclei slam into each other the subsequent residual particles have a much greater spread of energies than is the case with mere protons. This suggests that some collective effect is at work. The sulphur beam at CERN has an energy of 200 GeV per nucleon or a whopping 6.4 TeV per sulphur atom. Using like-mass nuclei insures that many of the nucleons in each nucleus will take part in the collision process and not stand idly by as "spectators," at least for "central" events in which the nuclei hit nearly dead on. In many experiments light projectiles are aimed at heavy- nuclei targets, with the result that the projectile passes through the target like a bullet, interacting with only a few nucleons along the way. Presently experiments at Brookhaven and CERN will use even heavier nuclei, such as gold and lead. (J. Bachler et al., Physical Review Letters, 7 Mar. 1994.)