Introduction

Spectroscopic study of $\Lambda$ hypernuclei through 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-flipped $\Lambda$ hypernuclear states and produces neutron rich $\Lambda$ hypernuclear 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 the high-quality primary beam.

The energy resolution of sub-MeV is a key to develop the 21st century hypernuclear spectroscopy. To this end, the first (e,e'K$^+$) hypernuclear spectroscopy experiment was carried out successfully at Jlab Hall C in the spring of 2000 under the E89-009 collaboration. This pioneering experiment demonstrated a great potential of the (e,e'K$^+$) reaction, obtaining a hypernuclear mass spectrum with the energy resolution of about 600 keV (FWHM) in the $^{12}$C(e,e'K$^+$) $^{12}_{\Lambda }$B reaction. However, it was also made clear that the improvement of the 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 proposed a new research program, "Investigation of $\Lambda$ hypernuclei by electromagnetic probes" (principal investigator: Osamu Hashimoto) to Monkasho (ministry of education, culture, sports, science and technology) of Japan. The proposal was approved as a "specially promoted research" under grant-in-aid for scientific research for the period from April 2000 to March 2004. The research program aims twofold goals: 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 with a newly designed kaon spectrometer and an improved experimental configuration was submitted. The new kaon spectrometer for the proposed experiment was designed to realize a large detection efficiency and high momentum resolution. The new experimental configuration allows us to avoid the most serious background due to very forward electrons associated with bremstrahlung process and, thus, to accept much higher beam intensity. 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 setup.

The construction of the kaon spectrometer magnets is now in progress. Some of the detectors are already in construction stage and the other in R&D. By the beginning of 2003, the total spectrometer system (including both magnets and detectors) is scheduled to be ready for installation in the Jlab experimental hall, either Hall A or C. The collaboration intends to take the first data of the E01-011 experiment in 2003.

This document was prepared for the first readiness review by the committee (chaired by Dr. R. Carlini) and describes the preparation status of the E01-011 experiment, the design and construction of the spectrometer system as of November 2001.