Particle Production at High Transverse Momentum in Nucleus-Nucleus Collisions at the AGS.

Measurements of particle production in 14.6 A cdotGeV/c Si + A and O + A collisions at high transverse momenta and at the nucleon-nucleon center -of-mass rapidity (y_{rm nn} ) were made by Experiment 802 at the Brookhaven National Laboratory Alternating Gradient Synchrotron. The particles were measured using a large-acceptance magnetic spectrometer and the Cherenkov Complex, a small acceptance arm of the spectrometer which provided particle identification at high momentum. The data presented in this thesis cover the transverse momentum (p|) range 0.7 to 3.2 GeV/c. The proton p|^ectra extend 0.5 GeV/c beyond the nucleon-nucleon kinematic limit and the pion spectra extend to the kinematic limit. The inclusive, invariant cross-sections for all measured particles are well described by exponentials in transverse mass, m|, over the entire measured momentum range, even beyond the kinematic limit. There is a systematic increase of the inverse slope of the m|^ectra with increasing target thickness and increasing centrality of the collisions, but the inverse slopes generally saturate with increasing centrality. The transverse mass spectra from p-p collisions, with the differences appearing only in the slopes of the m| exponentials. The K/ pi ratios at y_{rm nn} show an increase over the p-p and p-A measurements at all p| or m | values. The shapes of the Si + A K/ pi ratios are qualitatively the same as the shapes of the p-p K/pi ratios. The inclusive cross-sections and inclusive particle yields are both well described by a power-law dependence on the target mass. No evidence for saturation of particle production with increasing target thickness is seen at y_{rm nn}. The power-law exponents obtained from the Si-A yields compare extremely well to p-A measurements. The Si + A pion cross-sections are compared with pion cross-sections from p-p collisions expressed in terms of p|^2. The pion cross -sections in this variable show possible multi-component behavior, with some p-p measurements attributing two of the components of pion production from baryon resonance decay and meson resonance decay. The peripheral Si + Al p|^2 cross-sections compare extremely well to the p-p cross-sections and show the same multi-component behavior with slopes identical to those seen in p-p collisions. The inclusive cross-sections also show similar behavior, but with modifications seen in the high p| region and in the low -p| component (attributed to baryon resonance decays). In general, the global features of the transverse cross-sections in A-A collisions appear little different than those seen in p-p or p-A collisions. However, the observed increase in the K/pi ratio in Si + A collisions remains to be understood. This experimental result continues to be the most significant difference between p-p and A-A collisions observed at AGS energies. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253 -1690.).