G. P. Capitani

The reaction $e\overrightarrow{p}{e}^{\prime }{K}^{+}\Lambda \mathrm{}\left(1520\right)\mathrm{}$ with $\Lambda \mathrm{}\left(1520\right)\mathrm{}\to p^{\prime }{K}^{-}$ was studied at electron beam energies of 4.05, 4.25, and 4.46 GeV, using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The $\cos {\theta }_{K^{+}},$ ${\phi }_{K^{+}},$ $Q^2,$ and W dependencies of $\Lambda \mathrm{}\left(1520\right)\mathrm{}$ electroproduction are presented for the kinematic region $0.9<\mathrm{}{Q}^2<2.4\mathrm{}\hspace{0.5em}{\mathrm{GeV}}^2$ and $1.95<W<\mathrm{}2.65\mathrm{}\hspace{0.5em}\mathrm{GeV}.$ Also, the $Q^2$ dependence of the $\Lambda \mathrm{}\left(1520\right)\mathrm{}$ decay angular distribution is presented for the first time. The $\cos {\theta }_{K^{+}}$ angular distributions suggest t-channel diagrams dominate the production process. Fits to the $\Lambda \mathrm{}\left(1520\right)\mathrm{}$ t-channel helicity frame decay angular distributions indicate the $m_z=\pm \frac{1}{2}$ parentage accounts for about 60% of the total yield, which suggests this reaction has a significant contribution from t-channel processes with either ${\mathit{K}}^{+}$ exchange or longitudinal coupling to an exchanged ${\mathit{K}}^{*}.$ The $Q^2$ dependence of the $\Lambda \mathrm{}\left(1520\right)\mathrm{}$ production cross section is the same as that observed for $\Lambda \mathrm{}\left(1116\right)\mathrm{}$ photo- and electroproduction.

Differential cross sections for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(γ,p)n reaction were measured at five laboratory angles from 32.5° to 130°, for photon energies between 100 and 255 MeV, in 10 MeV steps. A quasi-monochromatic photon beam, obtained by positron in-flight annihilation on a liquid hydrogen radiator, was used, and the photon spectrum was measured on-line by a pair spectrometer. The normalization uncertainty is within ±5%. Data agree, within the total errors, with recent results of a tagged-photon experiment and of a measurement of the inverse process. The measured angular distributions were fitted by a sum of Legendre polynomials, and the results compared with recent calculations. Significant departures from the calculated angular distribution asymmetry have been found.