|2000 JLab News Release|
Jefferson Lab Hypernuclear Experiment Completed
Experimenters have completed the first hypernuclear study to use the high-intensity, continuous electron beam of Jefferson Lab's CEBAF accelerator. Conventional nucleons plus one or more strange-quark-containing hyperons make up a hypernucleus. At the hadron level, such systems provide a new many-body spectroscopy, where dynamical symmetries may appear that are forbidden in ordinary nuclei by the Pauli Principle. Thus a hypernucleus allows exploration of new dimensions of the hadronic many-body problem.
The Jefferson Lab experiment provided an energy resolution more than a factor of two better than had been achieved heretofore, and demonstrated that the CEBAF beam quality would permit future experiments to achieve energy resolution in hypernuclear spectroscopy an order of magnitude better than in previous work. Experiments in which the hypernucleus is created by electroproduction are also complementary to those involving hadron production in that states with different spins and parities are produced preferentially with each of the two techniques.
The experiment, titled an "Investigation of the Spin Dependence of the
Lambda N Effective Interaction in the P Shell," took place from February
to May in Hall C. Data analysis is under way. Hall C was designed to
accommodate specially configured experiments like this one. The study
required construction of a new, special-purpose instrument called the
hypernuclear spectrometer system (HNSS) for the tracking of up to 200
million particle interactions per second and isolating the much rarer
hypernucleus-forming hyperonic events, which ocurred at a rate of a few
per hour. Nearly 100 researchers from 14 institutions in the U.S. and
four other countries collaborated to conduct the experiment.
Co-spokespersons are L. G. Tang of Hampton University, E. Hungerford of
the University of Houston, and R. E. Chrien of Brookhaven National