T. Sung

Centrality dependence of kaon yields in Si + A and Au + Au collisions at the AGS

Charged kaon production has been measured in Si+Al and Si+Au collisions at 14.6 A GeV/c, and Au+Au collisions at 11.1 A GeV/c by Experiments 859 and 866 (the E--802 Collaboration) at the BNL AGS. Invariant transverse mass spectra and rapidity distributions for both K+ and K- are presented. The centrality dependence of rapidity-integrated kaon yields is studied. Strangeness enhancement is observed as an increase in the slope of the kaon yield with the total number of participants as well as the yield per participant. The enhancement starts with peripheral Si+Al and Si+Au collisions (relative to N+N) and appears to saturate for a moderate number of participating nucleons in Si+Au collisions. It is also observed to increase slowly with centrality in Au+Au collisions, to a level in the most central Au+Au collisions that is greater than that found in central Si+A collisions. The enhancement factor for

System, centrality, and transverse mass dependence of two-pion correlation radii in heavy ion collisions at 11.6A and 14.6A GeV/c

K^+

Recent results from E802 and E859

production are 3.0 +-0.2(stat.) +-0.4(syst.) and 4.0 +-0.3(stat.) +-0.5(syst.), respectively, for the most central 7% Si+Au collisions and the most central 4% Au+Au collisions relative to N+N at the correponding beam energy.

Production of phi mesons in central 28Si+196Au collisions at 14.6A GeV/c.

Two-pion correlation functions are analyzed at mid-rapidity for three systems (14.6 A-GeV Si+Al, Si+Au, and 11.6 A-GeV Au+Au), seven distinct centrality conditions, and different kT bins in the range 0.1--0.5 GeV/c. Source reference frames are determined from fits to the Yano-Koonin source parameterization. Bertsch-Pratt radius parameters are shown to scale linearly with both number of projectile and total participants as obtained from a Glauber model calculation. A finite emission duration that increases linearly with system/centrality is also reported. The mT dependence of the Bertsch-Pratt radii is measured for the central Si+Au and Au+Au systems. The system/centrality dependence is investigated separately for both high and low mT regions.

Global transverse energy distributions in Si+Al, Au at 14.6A GeV/c and Au+Au at 11.6A GeV/c

Abstract Recent single-particle inclusive measurements and two-particle correlation data from E802 and its succesor, E859, are presented. The K + / π + ratio observed for collisions of 14.6 A·GeV 28 Si ions on various targets is presented as a function of both forward and transverse energy. Source sizes are determined via interferometry using π + , π − , K + and proton pairs.

Recent results from experiment 859 at the BNL AGS

Production of the {phi} meson in central Si+Au collisions has been measured by E859 at the Brookhaven Alternating Gradient Synchrotron by selecting events with identified K{sup +}K{sup -} pairs. The mass and width of the {phi}, obtained from the invariant mass distribution of kaon pairs, are consistent with those of free f mesons. The transverse mass and rapidity distributions are presented. The inverse slope parameter for an exponential fit to the invariant transverse mass distribution is 179{+-}10{+-}17 MeV.

Backward emission of protons in Au+Au collisions at 11.7 A.GeV/c

Abstract Measurements of the global transverse energy distributions dσ / dE T and dE T / dη using the new AGS beam of 197 Au at 11.6 A GeV/ c on a Au target, as well as a beam of 28 Si at 14.6 A GeV/ c on Al and Au targets, are presented for a leadglass detector with acceptance 1.3 ≤ η ≤ 2.4 and 0 ≤ φ π . The dσ / dE T spectra are observed to have different shapes for the different systems and simple energy rescaling does not account for the projectile dependence. The Au+Au dσ / dE T spectrum is satisfactorily constructed from the upper edge of Si+Au by the geometric Wounded Projectile Nucleon Model after applying a correction for the beam energy.

Target rapidity proton distributions for SI+A collisions at the AGS

Abstract This paper presents recent results from Experiment 859 at the BNL AGS, focussing on strangeness ( K ± , Λ, Λ ), rare probes ( p , φ) and two-particle correlations. Highlights of the paper include an analysis of the centrality dependence of K ± yields in terms of the number of participants, a brief review of the current status of the E859 Λ and Λ data, an analysis of the target dependence of p yields in terms of p K − ratios, results of a re-analysis of Λ feed-down contamination of p s, a comparison of the cenal SiAu and pp φ yields through the φ K − ratio, an extremely preliminary study of the centrality dependence of the φ line-shape, a summary of the centrality dependence of two-π correlation source sizes, and a comparison of results from two-dimensional analyses of the two-π and two-K + correlation functions.

Production ofφMesons in CentralS28i+A196uCollisions at14.6AGeV/c

We present preliminary results for the emission of target rapidity protons in minimum bias and central 11.7 A.GeV/c Au+Au collisions. The data span the pseudo-rapidity range {vert_bar}{eta}{vert_bar} {le} 0.76 and proton kinetic energy range of 50 {le} E {le} 200 MeV. The slopes of the kinetic energy spectra and dN/d{eta} values for central and minimum bias collisions are strikingly similar. Comparison of the results to results for Si+Au and p+A shows that the shape of the dN/d{eta} distribution is independent of the reaction system or centrality suggesting that the spectator matter does not play a decisive role in determining the shape of the proton distributions at back angles for these systems at AGS energies.

The centrality dependence of the source size for AuAu collisions at the AGS

Preliminary results are presented for the production of protons in 14.6 A{center dot}GeV/c Si+Al and Si+Au collisions measured by the E859 Phoswich Array at the BNL AGS. The proton data presented cover the laboratory angles of 50--130 degrees and kinetic energies of 40--180 MeV. Slopes and integrated distributions are extracted and comparisons with other experimental data are discussed.