This page provides information on Jefferson Lab Hall A experiments E94-107, "High Resolution 1p-Shell Hypernuclear Spectroscopy" and to a lesser degree links to E98-108, "Electroproduction of Kaons up to Q2 = 3 (GeV/c)2".
Proposal E94-107 measures hypernuclear production from p-shell nuclei. Using an electromagnetic probe, the production of a Lambda-hyperon occurs off of a proton and leads to a final state where the Z is reduced by one: AZ(e,e'K)AZ-1 (this is in contrast to kaon or pion beams where the reaction happens from inital-state neutrons). The shell level spacings of the resultant hypernuclei are sensitive to the details of the hyperon-nucleon potential. In this case, we are using the energy resolution of the Hall A spectrometers to get information on the spin-orbit splitting.
The experiment is challenging because of the low production rates, the high backgrounds, and the tight tolerances on the knowledge of the incident and final energies and angles. A new RICH detector was built, along with an improved, highly segmented scintillator (S2m) and two renovated diffusion aerogel detectors to perform particle identification.
Proposal E98-108 measured kaon production cross sections, picking a specific reaction mechanism via a separation of response functions in the exclusive H(e,e'K+)Y reaction. This experiment focussed on how kaons are electromagnetically produced -- meaning which production mechanisms contribute and to what extent. The t-channel production, where the virtual photon scatters "quasifree" on the kaon was emphasized in order to maximize sensitivity to the kaon internal structure.
Current knowledge is unsatisfactory. Unseparated cross sections have been used to constrain the kaon form factor, but these experiments rely upon the t-channel dominating the cross section. We know from other experiments that in this W region, Lamba production seems dominated by t-channel production and Sigma production seems dominated by s-channel resonances.
You can find the most
current results of the E98-108 experimental analysis at
A good list of on-line
references is available which describes the theoretical efforts
to predict hypernuclear behavior and past attempts to measure that
Pete Markowitz - firstname.lastname@example.org
A good list of on-line references is available which describes the theoretical efforts to predict hypernuclear behavior and past attempts to measure that same behavior.