Photoproduction ofK+Mesons in Hydrogen

$K^{+}$ mesons produced in a liquid hydrogen target bombarded by the 1100-Mev bremsstrahlung of the California Institute of Technology synchrotron have been observed. It has been found that the $K^{+}$ mesons are produced in association with ${\Lambda }^0$ hyperons, in accordance with the law of associated production of strange particles. The $K^{+}$ mesons were momentum-analyzed in a magnetic spectrometer and identified by their energy loss in three scintillation counters, the very large background due to pions and protons being virtually eliminated by means of time-of-flight discrimination. The differential cross section for the reaction $\gamma +p\to K^{+}+{\Lambda }^0$ has been measured at photon energies of 960 Mev, 1000 Mev, and 1060 Mev at various $K^{+}$-meson laboratory angles between 15 degrees and 45 degrees. This cross section shows little variation with photon energy between 960 Mev and 1060 Mev or with center-of-momentum angle over the range investigated.