H.C. Britt

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

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.

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

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.

Au+Au reactions at the AGS: Experiments E866 and E917

Particle production and correlation functions from Au+Au reactions have been measured as a function of both beam energy (2--10.7 AGeV) and impact parameter. These results are used to probe the dynamics of heavy-ion reactions, confront hadronic models over a wide range of conditions and to search for the onset of new phenomena.Particle production and correlation functions from Au+Au reactions have been measured as a function of both beam energy (2-10.7AGeV) and impact parameter. These results are used to probe the dynamics of heavy-ion reactions, confront hadronic models over a wide range of conditions and to search for the onset of new phenomena.

Composite charged particle detectors with logarithmic energy response for large dynamic range energy measurements

Abstract We have developed an array of detectors to identify charged particles produced in heavy ion reactions. The array, which consists of eight individual detector modules and a forward hodoscope, subtends a solid angle of 0.58π and covers 62% of the reaction plane in laboratory coordinates. Each of the eight identical modules has an active area which extends 13° above and below the array plane with additional limited coverage between 13° and 26°. Each module measures the position, energy and velocity of charged particles over a dynamic range which extends from minimum ionizing protons with energies up to 200 MeV to highly ionizing fission fragments with Coulomb-like energies. Position and time-of-flight are measured with low pressure multiwire proportional counters (MWPC). Total energies for heavier ions are obtained from large ion chambers. Energy and position measurements for more energetic lighter ions which pass through the ion chambers are made with segmented phoswich arrays. The forward angle hodoscope is a 34-element array of phoswich detectors mounted symmetrically around the beam axis. These detectors are sensitive to beam velocity particles ( E / A > 10–40 MeV / A ) and capable of elemental resolution from protons to Z = 23.

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

Recent results from experiment 859 at the BNL 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.

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

Particle production at the AGS: an excitation function

Abstract Experiments E866 and E917 at the AGS have measured the differential invariant yields of positive and negative charged kaons from Au+Au collisions at beam kinetic energies in the laboratory of 2, 4, 6, 8, and 10.8 A·GeV. At each beam energy, a multiplicity array is used to select on the centrality of the collision.

Strangeness production in high density baryon matter

Strangeness production in heavy-ion collisions, when compared to proton proton collisions, is potentially a sensitive probe for collective energy deposition and therefore for reaction mechanisms in general. It may therefore provide insight into possible QGP formation in dense nuclear matter. To establish an understanding of the observed yields, a systematic study of high density baryon matter at different beam energies is essential. This might also reveal possible discontinuities in the energy dependence of the reaction mechanism. We present preliminary results for kaon production in Au+Au collisions at beam kinetic energies of 6, 8, and 10.7 GeV/u obtained by the E917 experiment at the AGS (BNL). These measurements complement those carried out by the E866 collaboration at 2, 4, and 10.7 GeV/u with a significantly enlarged data sample. In both experiments a large range of rapidities was covered by taking data at different angular settings of the magnetic spectrometer.Strangeness production in heavy ion collisions, when compared with proton-proton collisions, is potentially a sensitive probe for collective energy deposition and therefore for reaction mechanisms in general. It may therefore provide insight into possible quark-gluon plasma formation in dense nuclear matter. To establish an understanding of the observed yields, a systematic study of high density baryon matter at different beam energies is essential. This might also reveal possible discontinuities in the energy dependence of the reaction mechanism. We present preliminary results for kaon production in Au + Au collisions at beam kinetic energies of 6, 8, and 10.7 GeV/u obtained by the E917 experiment at the AGS (BNL). These measurements complement those carried out by the E866 Collaboration at 2, 4, and 10.7 GeV/u with a significantly enlarged data sample. In both experiments a large range of rapidities was covered by taking data at different angular settings of the magnetic spectrometer.