The Role of 'Additive Quark' Dynamics in Stopping and Strangeness Production in Nuclear
Collisions at the AGS
by
Brian A. COLE (Columbia University, New York, USA)
→
Europe/Zurich
CERN
CERN
Description
Experiment 910 at the Brookhaven National Laboratory AGS accelerator has studied proton-Be, Cu, and Au collisions at beam energies of 12 and 18 GeV/c. The experiment has focussed on the study of the change in the dynamics of p-A collisions with centrality using the multiplicity of 'grey' tracks and the estimated number of collisions suffered by the projectile proton as a measure of centrality. We observe rapid 'stopping', with the projectile proton losing two units of rapidity in central p-Be collisions, but observe none of the
expected effects of this stopping in the production of secondary particles. We observe scaling between AGS and higher energies in the production of energetic pions in peripheral collisions and show that the spectra of these pions are consistent with the momentum
distribution of valence quarks within the proton. In central p-Au collisions we observe a much softened pion spectrum consistent with the fragmentation of all valence quarks in the proton. These data, together with measurements of the centrality dependence of pion and
strange particle multiplicities give strong evidence for 'additive quark' behaviour in p-A collisions at the AGS. We investigate the implications of these results for interpreting data from heavy ion collisions, particularly focussing on the physics of strangeness
enhancement.
