H.Z. Huang

A Single arm spectrometer detector system for high-energy heavy ion experiments

The recent availability of 14.6 GeV/c per nucleon 16O and 28Si ions from the Brookhaven National Laboratory Tandem-AGS accelerator facility has prompted the design, construction and operation of a large-solid-angle (25 msr) magnetic spectrometer with particle identification from ∼0.5 to ∼4.7 GeV/c. A small-solid-angle Cherenkov counter complex views the target through the magnet and extends the particle identification up to ∼15 GeV/c. This experiment (E-802) employs event characterization detectors, a charged-particle multiplicity array, a highly segmented lead-glass detector, and a zero degree calorimeter. The facility measures momentum spectra of identified heavy-ion-produced hadrons with high resolution (Δp/p≤0.005) as a function of collision centrality given by triggers from the event characterization detectors. Construction and performance details of the spectrometer components and auxiliary detectors are described.

Recent results from E802 and E859

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.

Antiproton production in 14.6 AGeVc Si+A collisions

Abstract Antiproton production cross sections have been measured for minimum bias and central Si+Al and Si+Au collisions at 14.6 A GeV c . The data presented cover the range of transverse momentum from 0.3 to 1.2 GeV c and lab rapidities from 1.1 to 1.7 units. The relative p π − and p K − yields are found to be the smallest for the heaviest system measured, central Si+Au collisions. For these collisions, the p π − ratio, determined from integrated yields for 1.1⩽y⩽1.7, is (0.84±0.07)×10−3. In the same rapidity interval, the average antiproton inverse m⊥ slope is 141±14 MeV for central Si+Al and central Si+Au collisions.

Measurement of energy and charged particle emission in the central rapidity region from O+A and p+A collisions at 14.5 GeV/c per nucleon and preliminary results from Si+A collisions

The first data from a16O beam of total energy 232 GeV at the BNL Tandem-AGS are discussed. Preliminary results from a28Si beam of total energy 406 GeV are also shown. The full complement of E802, including a magnetic spectrometer, was used for the28Si measurement. A different experimental arrangement was used for16O. Comparison measurements with proton beams are presented for both configurations.

Centrality dependence of K+ and π+ multiplicities from Si + A collisions at 14.6 A GeV/c☆

Abstract K + and π + multiplicities have been measured in magnetic spectrometer for Si++ Al, Si+ Cu and Si + Au collisions at 14.6 A GeV/ c incident momentum. The multiplicities were obtained for five different windows of forward kinetic energy as detected in a zero degree calorimeter. The K + / π + multiplicity ratio ranges from ≈9% in peripheral interactions to 19% in central Si+Au. The largest K + / π + ratios are observed for those events for each target that leave the least energy in the zero degree calorimeter and the ratio increases with target mass. The observations suggest that multiple interactions are important in the particle production mechanism.

Target rapidity proton distributions for SI+A 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.

Particle production in pA and AA collisions at AGS

Production of light particles (π±,K±,p) has been measured in both Si+A and p+A collisions. Several interesting features have been observed, among which are: the enhanced K+/π+ ratio and the larger 〈mt〉 for K+ and proton. Comparisons between ≊pp, pA and SiA collisions are discussed.

Spectrometer results from BNL E802

Measurements of collisions of 14.5 GeV/c per nucleon 28Si ions with nuclear targets using the BNL E802 spectrometer are presented. A description of the experiment and preliminary particle ratios are discussed.