Measurement of polarisation observables in $K^0_sSigma^+$ photoproduction off the proton

The reaction $gamma , p rightarrow K^0_S,Sigma^+$ is studied in the photon energy range from threshold. Linearly polarised photon beams from coherent bremsstrahlung enabled the first measurement of photon beam asymmetries in this reaction up to $E_gamma = 2250$ MeV. In addition, the recoil hyperon polarisation was determined through the asymmetry in the weak decay $Sigma^+ rightarrow p pi^0$ up to $E_gamma = 1650$ MeV. The data are compared to partial wave analyses, and the possible impact on the interpretation of a recently observed cusp-like structure near the $K^*$ thresholds is discussed.