Measurement of $\gamma p \rightarrow K^ + \Lambda$ and $\gamma p \rightarrow K^ + \Sigma^0$ at photon energies up to 2.6 GeV

Abstract.The reactions $\gamma p \rightarrow K^ + \Lambda$ and $\gamma p \rightarrow K^ + \Sigma^0$ were measured in the energy range from threshold up to a photon energy of 2.6 GeV. The data were taken with the SAPHIR detector at the electron stretcher facility, ELSA. Results on cross-sections and hyperon polarizations are presented as a function of the kaon production angle and the photon energy. The total cross-section for $\Lambda$ production rises steeply with energy close to threshold, whereas the $\Sigma^0$ cross-section rises slowly to a maximum at about $E_\gamma = 1.45$ GeV. Cross-sections together with their angular decompositions into Legendre polynomials suggest contributions from resonance production for both reactions. In general, the induced polarization of $\Lambda$ has negative values in the kaon forward direction and positive values in the backward direction. The magnitude varies with energy. The polarization of $\Sigma^0$ follows a similar angular and energy dependence as that of $\Lambda$, but with opposite sign.