Spectroscopic investigation of Λ hypernuclei in the wide mass region using the ( e , e ’ K + ) reaction

This proposal is an extension request of the partially approved proposal of JLab E01-011. The experimental goal of the E01-011 experiment was to prove the effectiveness of (e, e’K) hypernuclear spectroscopy by employing the “tilt method” for the electron arm and by installing a new high-resolution kaon spectrometer (HKS) for the kaon arm. It was intended to perform a spectroscopic study of Λ hypernuclei for the wide mass region using the (e, e’K) reaction, particularly beyond the p-shell region. The E01-011 experiment is on the commissioning stage in Hall C when this proposal is submitted. Considering the present status of the E01-011 experiment, we are now confident that we can extend the (e, e’K) hypernuclear spectroscopic study toward medium-heavy Λ hypernuclei. The expected results from the proposed experiment will provide Λ hypernuclear excitation spectra with the best energy resolution ever achieved in the reaction spectroscopy. An energy resolution of a few hundred keV and high statistical accuracy of the obtained spectra will clarify the single-particle behavior of a Λ hyperon in a medium-mass nuclear system. These high-quality data will greatly stimulate investigation of baryonic many-body system which has strangeness degree of freedom, the effective Λ-N interaction and ls splitting in the heavier hypernuclei beyond the p-shell. The experiment will take full advantage of high quality electron beam only available at JLab. The (e, e’K) reaction has unique characteristics as outlined below: • A proton is converted to a Λ hyperon. • Spin-stretched states are populated with both spin-flip and spin-non-flip amplitudes. • Reaction spectroscopy with resolution as good as 300 keV (FWHM) can be realized. The proposed experiment has two goals: 1. Excitation spectra of medium-heavy Λ hypernuclei will be studied using the V(e,e’K) Λ Ti reaction, following the Si(e,e’K) Λ Al reaction to be studied in the running E01-011 experiment. These spectra will provide precision binding energies and widths for the Λ hyperon in various orbits in the nuclear masses up to A = 89. The