P. J. Lindstrom

Relativistic Interaction of 22Ne and 26Mg in Hydrogen and the Cosmic-Ray Implications

The isotopic production cross sections for 22Ne projectiles at 377,581, and 894 MeV nucleon-1 and 26Mg projectiles at 371 and 576 MeV nucleon-1 interacting in a liquid hydrogen target have been measured by the Transport Collaboration at the Lawrence Berkeley Laboratory Heavy-Ion Spectrometer System (LBL HISS) facility. These cross sections are compared with those predicted by semi-empirical formulae. The systematics are studied to develop suitable inputs for calculations of galactic cosmic-ray interstellar transport. These calculations are used to unfold the transport effects from available observations of cosmic-ray CNO isotopes to extract the underlying source composition. With these new cross section measurements, the previously reported enhancement of 18O at the cosmic-ray source, which is sensitive to the cross sections for production from 22Ne and 26Mg and the uncertainties in cross section prediction formulae, may be explained. There is no evidence for an enhancement of 18O when these new cross sections are used in a weighted slab propagation calculation.

An update on the strangeness production measurements and H0 di-baryon search as performed by the AGS experiment 896

E896 was designed to search for the predicted short-lived six-quark H0 di-baryon. The goal is to enhance the existing knowledge by extending the search into regions of shorter lifetimes (approximately half that of the lambda) and via exploring a new creation channel, that of the coalescence of two lambdas. Two main tracking chambers are used, a distributed drift chamber positioned to measure low-pt and high-rapidity neutral particle decay products and a silicon drift detector array which measures particle production at mid-rapidity. Both detectors are also investigating lambda polarization, over their respective coverages, for Au-Au collisions at 11.3 GeV/nucleon. The current status of the H0 di-baryon search and preliminary results of the strange particle production and polarization measurements will be presented.

First results from the H0 di-baryon search and hyperon production measurements by the AGS Experiment 896.

Abstract The AGS Experiment 896 was designed to study strangeness production in Au—Au collisions at 11.6A GeV/c, in particular the formation of a six-quark di-baryon the H 0 . Heavy ion collisions provide favorable conditions for the H 0 formation either via coalescence of two Λ particles (owing to the large Λ production cross section) or direct production from the possible formation of a quark-gluon plasma. E896 also measured strange meson and baryon distributions from mid-rapidity. Preliminary results from this experiment are presented as well as details of the expected sensitivity for the H 0 search.

p and d production in relativistic heavy ion collisions: Results of BNL-E858

Abstract The production of long-lived negative secondaries, including π − , K − , antiprotons ( p ) and antideuterons ( d ) at 0° in Si+Au, Si+Cu, and Si+Al collisions at the BNL-AGS has been measured using a double-bend, double-focussing spectrometer. The p rapidity spectra from all three targets are well fit by Gaussians centered ( y = 1.7 − 1.8 ) at mid-rapidity, and are consistent with production in nucleon-nucleon first collisions. The d p 2 ratio in Si+Au collisions is lower by a factor of 10 than that seen in p+p and p+A collisions.

Design of the Bevalac heavy ion spectrometer system and its performance in studying 12C fragmentation

Abstract A description is given of the design and operation of the Heavy Ion Spectrometer System (HISS) at the Lawrence Berkeley Laboratory Bevalac. The general characteristics of the apparatus, which include a large superconducting magnet with drift chambers before and after for precise angle and momentum analysis of high multiplicity events and a large scintillation array for charge and velocity measurements, are explained. The performance of each part as measured in a 12 C fragmentation experiment is discussed in detail. The main feature of the data-acquisition and apparatus-monitoring systems and of the off-line event reconstruction are given.

Distributed drift chamber design for rare particle detection in relativistic heavy ion collisions

This report describes a multi-plane drift chamber that was designed and constructed to function as a topological detector for the BNL AGSE896 rare particle experiment. The chamber was optimized for good spatial resolution, two track separation, and a high uniform efficiency while operating in a 1.6 Tesla magnetic field and subjected to long term exposure from a 11.6 GeV/nucleon beam of 10**6 Au ions per second.

Neutron production in coincidence with fragments from the 4Ca+H reactions at Elab=357 and 565 A MeV

In the frame of the Transport Collaboration neutrons in coincidence with charged fragments produced in the 40Ca+H reaction at Elab=357 and 565 A MeV have been measured at the Heavy Ion Spectrometer System (HISS) facility of the Lawrence Berkeley National Laboratory, using the multifunctional neutron spectrometer MUFFINS. The detector covered a narrow angular range about the beam in the forward direction (0°–3.2°). In this contribution we report absolute neutron production cross sections in coincidence with charged fragments (10⩽Z⩽20). The neutron multiplicities have been estimated from the comparison between the neutron cross sections, in coincidence with the fragments, and the elemental cross sections. We have found evidence for a pre-equilibrium emission of prompt neutrons in superposition to a ‘slower’ deexcitation of the equilibrated remnant by emission of nucleons and fragments, as already seen in the inclusive rapidity distributions.

Neutron Production from the 40 Ca + H Reaction at E lab = 357 and 565A MeV

Fragmentation processes in nuclear collisions at intermediate energies are currently among the most widely studied topics both from an experimental and a theoretical point of view. They are not only essential tools for studies of the nuclear equation of state (EOS)1, 2, 3, 4, 5 but are also of great interest in astrophysics6, 7.

High rate multiplicity detector for relativistic heavy-ion collisions

Abstract We have constructed and operated a detector to measure the multiplicity of secondary particles produced in nucleus-nucleus collisions in the E878 experiment at the Brookhaven National Laboratory AGS facility. We describe the operation and performance of the detector in a high rate Au beam environment, and interpret the multiplicity data in terms of the impact parameters of the nucleus-nucleus collisions.

Search for new negative particles produced in 14.6 A GeV/c Si+A interactions

Abstract We discuss an investigation of negative particle production in interactions of 14.6 A GeV/c 28Si with targets of Al, Cu, and Au at the Brookhaven National Laboratory AGS, experiment E858. The experiment was performed using a beamline spectrometer to measure cross sections for meta-stable negatively charged particles produced at 0° at rigidities from 2 GV to 8 GV. We report upper limits on the production of new particles in the mass to charge (A/Z) range from −1 to −6 and discuss a simple model for describing our sensitivity.