Photoproduction ofY*Resonances above 1800 MeV

Abstract

The photoproduction of ${K}^{+}$ mesons and hyperons with strangeness $S=\ensuremath{-}1$, in reactions of the type $\ensuremath{\gamma}+p\ensuremath{\rightarrow}{Y}^{*}+{K}^{+}$, has been studied in the ${Y}^{*}$ mass range 1800-2600 MeV with a missing-mass spectrometer by analyzing the structures in the ${K}^{+}$ yield as a function of the end point bremsstrahlung energy. The ${K}^{+}$ yield was observed at the laboratory angle of ${\ensuremath{\theta}}_{K}=10\ifmmode^\circ\else\textdegree\fi{}$ and at the ${K}^{+}$ momenta of 2.5 and 2.0 BeV/c. A fit to the ${K}^{+}$ yield curve suggests, in addition to a smooth background, resonancelike structure at 1820\ifmmode\pm\else\textpm\fi{}20, 2025\ifmmode\pm\else\textpm\fi{}20, 2250\ifmmode\pm\else\textpm\fi{}20, and 2530\ifmmode\pm\else\textpm\fi{}25 MeV. Widths and photoproduction cross sections for these states were measured.