The Hypernuclear Spectroscopy Program at Jefferson Lab*

The central question of nuclear science is the structure of nuclear matter. For a complete 

understanding of the evolution of nuclear matter in the universe, detailed 

knowledge is necessary not only for stable nuclei, but also increasingly for 

unstable and exotic nuclear matter. Nuclear matter containing strangeness is 

thought to play an important role in stellar objects like neutron stars. The 

knowledge of the underlying interaction between strange baryons (hyperons) and 

nucleons (protons and neutrons) is incomplete. A complete theory of 

baryon-baryon interactions in the context of the underlying QCD degrees of 

freedom, quarks and gluons, will ultimately also have to describe interactions 

with and between strange baryons. In the laboratory, these can be best studied 

by implanting hyperons in ordinary nuclei, thus converting them to hypernuclei. 

The high quality electron beam at Jefferson Lab allowed for the first time to 

study hypernuclei by (e,e'K$^+$) reaction spectroscopy. Six experiments on 

a number of light to medium heavy targets were conducted.

Currently, the hypernuclear spectroscopy system at Jefferson Lab is being 

upgraded to ensure compatibility with the higher beam energies after the 12 GeV 

upgrade. Four new experiments have already been approved.

They will measure the hyperhydrogen nuclei which will addresses charge symmetry 

breaking or isospin dependence. Spectroscopy 40K and 

48K hypernucllei will study the isospin dependence of the 3-body Lambda-nn 

force. Finally, a study on a lead target will provide data on an extended nucleus with large neutron excess; 

this is the closest approximation to neutron star matter than can be achieved 

in the laboratory.

In this talk, I will review the results from the previous program and conclude with an outlook 

on the future experiments.