Recent Heavy Ion Results from CERN (European Organization for Nuclear Research) and Brookhaven.

摘要

Results of the first round of ultrarelativistic heavy ion experiments at CERN and BROOKHAVEN are reviewed. The experiments measure global variables such as transverse energy and multiplicity to characterize the impact parameter of the collisions and compare with geometrical models of heavy ion collisions. Charged particle transverse momentum spectra are measured, and p-nucleus and nucleus-nucleus collisions look rather similar. The hardening of the spectrum at high p/sub t/, previously observed in p-nucleus, is also present in heavy ion collisions. Two-particle interferometry has been used to study the pion source in central collisions. For analysis of all pions pairs, this looks approximately like the tube cut through the target by the projectile, but mid-rapidity pion pairs indicate a large, nearly spherical, very chaotic source. Study of dimuon production in the J//psi/ mass region has shown a suppression of J//psi/ with respect to the continuum in central compared to peripheral collisions. This could be a signal of deconfinement, but careful studies are underway to determine the magnitude of such an effect from nuclear absorption. 28 refs., 14 figs. (ERA citation 14:005507)