California Institute of Technology
Ultra-Heavy Interactions Collaboration
(UHIC)
UHIC is a collaboration of groups at Caltech, Washington University, and the University
of Minnesota. We investigate charge-changing peripheral collisions of ultra-heavy
nuclei (Z > 40) at ~ 1 - 10 GeV/nucleon with targets of a variety of masses from H (Z = 1)
to Pb (Z = 92). Our instruments measure the charge of the largest fragments
of the beam particles from accelerator beams. Our motivations include application of
the cross sections for charge-changing interactions to cosmic-ray propagation, and
investigation of the role of electromagnetic forces in the nuclear physics of peripheral
collisions.
UHIC grew out of an earlier collaboration of the same institutions on the High-Energy
Astrophysical Observatory (HEAO) C3 Heavy Nuclei Experiment (HNE). For several years
after the reentry of HEAO in 1982, the HNE collaboration continued to measure the response
of similar instruments and the cross sections for charge-changing interactions of
heavy nuclei at the Lawrence Berkeley Laboratories' Bevalac particle accelerator. Among the
results from these experiments was an apparent strong energy dependence in the cross
sections.
When ultra-heavy beams became available at the Brookhaven
National Laboratory Alternating Gradient Synchrotron (AGS),
UHIC was formed to exploit the previously unavailable energy range of several GeV/nuc. Results
from fragmentation of a 10.6 GeV/nuc Au (Z = 79) beam are reported in Geer et al. We have just
completed (January 1996) a very successful run at the AGS using Au beams at closely spaced energies
from 0.9 GeV/nuc to 4 GeV/nuc. This run also provided an opportunity to test some scintillator
materials for the TIGER project.
UHIC Co-Investigators and Institutions
California Institute of Technology
University of Minnesota
Louisiana State University
Washington University
The UHIC experiment configuration for the 1996 Brookhaven AGS run. The ion chambers are
designated with I#, the Cherenkov detectors with C#, the multiwire proportional position-sensitive
counters with MW, and the TIGER test scintillator instruments with S#. The position of the
Pb degraders used to lower the energy of the beam in some runs is designated with D, and the
position of the automatic target changer is designated with T. In the 1996 BNL AGS run, we
investigated interactions of 0.9 - 4 GeV/nuc gold in CH2 and C targets (from which we can
obtain H cross sections), as well as Al, Cu, Sn, and Pb targets.
The analysis of the data from this run is being done at the University of
Minnesota. We expect the final cross section measurements to be ready
for the 1998 APS Spring Meeting
in Columbus, Ohio. A paper will be submitted to Physical Review C.
Further results on parametric fits for charge-changing cross sections
and on the effects of the new measurements on propagation calculations
will follow.
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Here is a list of publications from HEAO3 HNE and UHIC.
The Particle Data Group pages contain many links to data,
experiments, and particle information of interest.
jrc