[en] We are using the p(e,e'K⁺p)π^- reaction to perform a measurement of the induced polarization of the electroproduced L(1116) using its pπ^- parity-violating weak decay. This study uses the CEBAF Large Acceptance Spectrometer (CLAS) to detect the scattered electron, the kaon, and the decay proton over the kinematics 0.8 (le) Q² (le) 3.5 GeV², 1.6 (le) W (le) 3.0 GeV, and the full kaon CM angle range. In this experiment a 5.5 GeV electron beam was incident upon an unpolarized liquid-hydrogen target. The goal is to map out the kinematic dependencies for this polarization observable to provide new constraints for models of the electromagnetic production of K-hyperon final states. Along with previously published photo- and electroproduction cross sections and polarization observables from CLAS, SAPHIR, LEPS, and GRAAL, these data are needed in a coupled-channel analysis to identify previously unobserved s-channel resonances. Preliminary polarization results will be presented.

[en] Beam-recoil transferred polarizations for the exclusive e-vectorp→e^'K⁺Λ-vector,Σ-vector⁰ reactions have been measured using the Continuous Electron Beam Accelerator Facility's large acceptance spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. New measurements have been completed at beam energies of 4.261 and 5.754 GeV that span a range of momentum transfer Q² from 0.7 to 5.4 GeV², invariant energy W from 1.6 to 2.6 GeV, and the full center-of-mass angular range of the K⁺ meson. These new data add to the existing CLAS K⁺Λ measurements at 2.567 GeV, and provide the first-ever data for the K⁺Σ⁰ channel in electroproduction. Comparisons of the data with several theoretical models are used to study the sensitivity to s-channel resonance contributions and the underlying reaction mechanism. Interpretations within two semiclassical partonic models are made to probe the underlying reaction mechanism and the ss quark-pair creation dynamics.

[en] A Λ hypernuclear spectroscopic experiment, JLab E05-115 was performed at JLab Hall-C in 2009 by the (e, e′K⁺) reaction. Data of Λ hypernuclei with mass numbers from A = 7 to A = 52 were successfully taken, and the analyses are in progress. A polyethylene (CH₂) target was used as a proton target to calibrate energy scales, and to study elementary process of the p(e, e′K⁺)Λ, Σ⁰ reaction. A preliminary differential cross section of K⁺Λ electro-production at low Q²[∼0.01 (GeV/c)²] and at small kaon angles (cosθ^CM_K ∼0.97) is reported in the present article. (author)

[en] In this report, we present the energy calibration of the Hall B bremsstrahlung tagging system at the Thomas Jefferson National Accelerator Facility. The calibration was performed using a magnetic pair spectrometer. The tagged photon energy spectrum was measured in coincidence with e⁺e^- pairs as a function of the pair spectrometer magnetic field. Taking advantage of the internal linearity of the pair spectrometer, the energy of the tagging system was calibrated at the level of +/-0.1%E_γ. The absolute energy scale was determined using the e⁺e^- rate measurements close to the end-point of the photon spectrum. The energy variations across the full tagging range were found to be <3MeV