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Spectroscopic study of $\Lambda$ hypernuclei by the (e,e'K$^+$) reaction has unique advantages over those through meson-induced reactions such as ($\pi^+$, K$^+$) and (K$^-$, $\pi$). Contrary to the meson-induced reactions, the (e,e'K$^+$) reaction favorably excites spin-flip $\Lambda$ hypernuclear states and produces neutron rich $\Lambda$ hypernuclei converting a proton to a $\Lambda$ hyperon. From the experimental point of view, it is also of significant importance that the reaction allows us to improve the energy resolution down to sub-MeV taking advantage of a high-quality primary beam.

The sub-MeV energy resolution is a key for developing the 21st century hypernuclear spectroscopy program. To this end, the first (e,e'K$^+$) hypernuclear spectroscopy experiment was carried out successfully at Jefferson Lab's (Jlab) Hall C in the spring of 2000 by the E89-009 collaboration. This pioneering experiment demonstrated the great potential of the (e,e'K$^+$) reaction, obtaining a hypernuclear mass spectrum with an energy resolution of about 900 keV(FWHM) in the $^{12}$C(e,e'K$^+$) $^{12}_{\Lambda }$B reaction. However, it was also made clear that an improvement of this hypernuclear spectrometer system is vitally needed to fully explore the potential. In particular, it was recognized, even before the E89-009 experiment started, that a new high-efficiency high-resolution kaon spectrometer is required.

In the course of the above efforts, the Tohoku group of the collaboration submitted a new proposal, "Investigation of $\Lambda$ hypernuclei by electromagnetic probes" (Principal investigator: Osamu Hashimoto) to MEXT (Ministry of Education, Culture, Sports, Science and Technology:Monkasho) of Japan. The proposal was approved as a "specially promoted research project" under a grant-in-aid for scientific research for the period from April 2000 to March 2004. The research project has two main programs: 1) spectroscopic study of $\Lambda$ hypernuclei through the (e,e'K$^+$) reaction at Jlab, and 2) study of the strangeness production mechanism by measuring neutral kaons in the tagged-photon induced reactions at Laboratory for Nuclear Science, Tohoku University.

Based on these two recent developments, the once approved Jlab experiment E97-011 was revised and a new proposal assuming a new kaon spectrometer and a new improved experimental configuration was submitted. The proposed experiment was approved by the PAC19 in February 2000, and since then, the E01-011 collaboration group has been preparing the new experimental equipment.

For the proposed experiment, a new kaon spectrometer was designed with an intention to realize both large detection efficiency and high-resolution, simultaneously. At the same time, a new experimental configuration was adopted so that very forward electrons associated with bremsstrahlung process can be avoided and therefore a higher luminosity ($\propto$ target thickness $\times$ beam intensity) can be accepted. The construction of the spectrometer magnets was finished and the precise field map is now under way.

After the first readiness review (19th of November, 2001) chaired by Dr. R. Carlini, there has been considerable progress in optimization of the experimental condition as well as in detector development.

The spectrometer system (both magnets and detectors) is scheduled to be ready for installation in the Jlab experimental Hall-C anytime by the end of 2003. The collaboration would like to run the first part of the E01-011 experiment in 2004.

This document is prepared for the second readiness review committee chaired by Dr. R. Carlini which Hall C leader Dr. R. Ent charges to review the progress of the experimental preparation. The document describes the updated preparation status of the E01-011 experiment, the design and construction of the spectrometer system as of May, 2003.

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Satoshi N. Nakamura 平成16年12月1日