Previous E89-009 experiment

The first hypernuclear electro-production experiment has been successfully completed in Hall C at Jlab in the spring of 2000. This experiment used the $^{12}$C(e,e'K$^{+}$) $^{12}_{\Lambda }$B reaction, and observed the ground state peak of $^{12}_{\Lambda }$B hypernucleus. The experiment demonstrated that $\Lambda$ hypernuclear spectroscopy can be performed by the (e,e'K$^+$) reaction and that sub-MeV energy resolution can be obtained as shown in Fig. 4. The resolution obtained in the experiment, $\sim$ 650 keV, is better by a factor of 3 than that previously obtained.

The E89-009 experiment was designed to take advantage of the peak in the virtual photon flux at very forward angles. Thus it had low luminosity since a maximum number of photons/incident electron were available for reactions. The experimental setup is schematically shown in Fig. 5. Zero degree electrons and positive kaons were bent into their respective spectrometers on opposite sides of the beam by a splitter magnet. The electron momentum was analyzed by a small Split-Pole spectrometer positioned to detect zero degree electrons. Positive kaons were detected also at around 0 degrees using the SOS spectrometer. Typical count rates of each particle in the Enge and SOS spectrometers were summarized in section 14.4 of Appendix B. The experiment utilized a low beam current of 0.66 $\mu$A with a $^{12}$C target 20 mg/cm$^2$ thick.

Although the experiment was successful, the yields were limited due to the background flux of bremsstrahlung in the electron spectrometer. We had recognized that further improvement of experimental configuration would be required to extend these studies to heavier systems. However E89-009 was needed to provide valuable information on rates and cross sections in order to design a geometry which could be successfully be extended.