The Angular Dependence of 16 O ( e , e ′ K + ) 16 Λ N and H ( e , e ′ K + ) Λ ( Proposal to JLab PAC - 31 ) E . Cisbani

In all Jlab hypernuclear electroproduction experiments already performed (E89-009, E94107, E01-011) or approved (E05-015) the K mesons are detected at very small (few degrees) laboratory scattering angels (measured with respect to virtual photon momentum). This region of kaon scattering angles is not covered, unfortunately, by recent photoand electroproduction data on the elementary production process from CLAS, SAPHIR, and LEPS Collaborations. The angular dependences of the cross section at small angles and at photon energies Eγ ≈ 2 GeV predicted by different models for the K Λ electromagnetic production differ drastically and this lack of relevant information about the elementary process makes an interpretation of obtained hypernuclear spectra difficult. In addition, the ratio of the hypernuclear (calculated in DWIA) and elementary cross section measured at the same kinematics should be almost model independent at very forward kaon scattering angles. The ratio therefore contains direct information on the target and hypernuclear structure, production mechanisms and, possibly, on the modification of the dynamics of the elementary p(e, eK)Λ process in the nuclear environment. The Hall A experimental setup with septum magnets has a unique opportunity to solve the above mentioned problems using the waterfall target and virtual photons with energy Eγ∗ ≃ 2 GeV. We will measure: • the electroproduction cross section on the proton in H2O at LAB kaon scattering angels θ Ke = 8.5 o and 11 (θ Kγ = 4 o and 7) which together with our previous measurements for θ Ke = 6 o (θ Kγ = 2 ) will cover the angular region missing in CLAS and SAPHIR data. New precise data will clearly discriminate between various models of photoand electroproduction of strangeness, such as Saclay-Lyon and Kaon-MAID; • the angular dependence of the hypernuclear cross section (HN) on O will be determined simultaneously. These data and, especially, the ratio of HN to the elementary cross section will give new valuable information on hypernuclear structure (including spin assignment of produced hypernuclear states), reaction mechanisms and, may be, the modification of the dynamics of the (e, eK) process in the nuclear medium.