Differential cross sections for $\gamma p\to K^{+}\Lambda (1405)$ and $\gamma p\to K^{+}{\Sigma }^0(1385)$ reactions have been measured in the photon energy range from 1.5 to 2.4 GeV and the angular range of $0.8<\cos (\Theta )<1.0$ for the $K^{+}$ scattering angle in the center-of-mass system. This data is the first measurement of the $\Lambda (1405)$ photoproduction cross section. The line shapes of $\Lambda (1405)$ measured in ${\Sigma }^{+}{\pi }^{-}$ and ${\Sigma }^{-}{\pi }^{+}$ decay modes were different with each other, indicating a strong interference of the isospin 0 and 1 terms of the $\Sigma \pi$ scattering amplitudes. The ratios of $\Lambda (1405)$ production to ${\Sigma }^0(1385)$ production were measured in two photon energy ranges: near the production threshold ($1.5<E_{\gamma }<2.0$ GeV) and far from it ($2.0<E_{\gamma }<2.4$ GeV). The observed ratio decreased in the higher photon energy region, which may suggest different production mechanisms and internal structures for these hyperon resonances.

• Received 21 May 2008

DOI:https://doi.org/10.1103/PhysRevC.78.035202