Jefferson Laboratory experiment E91-016, ``Electroproduction of Kaons and Light Hypernuclei'' is a study of quasifree production of Kaons on targets of H, D, ³He, ⁴He, Carbon and Aluminum, at an incident electron energy of 3.245 GeV. For H and D targets, data were also obtained at E = 2.445 GeV. The scattered electron e¢ and emergent K⁺ were detected in coincidence with the use of the HMS and SOS spectrometers, respectively, in Hall C of Jefferson Laboratory. Angular distributions for the (e,e'K⁺)Y reactions were measured at forward angles with respect to the virtual photon for Q² @ 0.35 GeV². Particle identification utilizing time-of-flight detectors together with Aerogel Cerenkov detectors yields clean missing mass spectra [1], and allows subtraction of random backgrounds. The experiment was run in two time periods. The H and D targets were studied near the end of 1996 while the balance of the experiment, namely the ^3,4He targets were bombarded in the fall of 1999 when the FZR also collaborated on running the experiment. More than 1.4 TB of data were taken during that time.
The fundamental interaction being studied is N(e,e'K⁺)Y where Y is either a L or S and N represents a nucleon. For the H target, the final state can only be a L or S, but for heavier targets, there is relative motion between the nucleons in the target that results in broadening of the peaks. For the D target, it is possible to separate the two peaks inasmuch as the Fermi broadening is not large compared to the mass difference [2]. For ³He and ⁴He, very preliminary missing mass spectra being shown in Fig 1, it will be more difficult to separate the yields for the various final states. Even in this early stage of analysis, it is quite clear that the width of the quasifree peak is greater in ⁴He (more binding) than in ³He.

Fig. 1 Preliminary missing mass spectra for ³He and ⁴He(e,e¢K⁺) reactions for a relative angle of 0 deg in the lab between the virtual photon and the Kaon. The various Monte-Carlo simulations for the quasi-free contributions as well as their sum (solid line) are shown. They are preliminary and relatively crude. The location of ``bound L and S'' states is shown merely to suggest possible locations. It should be emphasized that much more analysis is required.

For D, it is known that there is no bound L-nucleon state, but for both ³He and ⁴He targets we anticipate evidence for a bound hypernuclear states. Although the data shown in the figure are quite preliminary, it appears that bound L hypernuclear states are seen. The possibility of bound S hyper-nuclei also exists, but it is conjectural at this time. Construction of an optimal Monte-Carlo simulation will require considerably more effort before any conclusions can be drawn. The large number of final state configurations results in complications that must be analyzed prior to extracting final cross sections.
Together with Carbon and Aluminum the complete data set contains five different targets and provides a high-statistics study of the mass dependence of Kaon electroproduction on light nuclei.

¹ FZR and Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
² presently Feodor Lynen Research Fellow at Argonne National Laboratory, Argonne,
Illinois 60439, USA References
[1]  ANL Annual Report # ANL99-12, Fig. III-6
[2]  D. Abbott et al., Nucl. Phys. A 639 (1998) 205c  IKH 05/31/01 © F. Dohrmann