Measurement of the single polarization observables I[sup c] and I[sup s] in π[sup 0]η photoproduction

Abstract

Meson photoproduction off the nucleon is a key tool in order to understand the structure of baryons and their excitation spectrum. Especially in the regime of high‐lying resonances the photoproduction of multi‐meson final states is of increasing importance, given that the cross sections for such processes exceed those for single‐meson production. Additionally it gives a handle on sequential decays of such resonances via e.g. the Δ(1232) or the S11(1535) in the intermediate state. For a complete understanding of the processes involved, the measurement not only of unpolarized cross sections but also of polarization observables is mandatory. With the Crystal Barrel/TAPS experiment, located at the ELSA accelerator facility in Bonn, it was possible to determine such observables using a linearly polarized photon beam impinging on a liquid hydrogen target. The beam asymmetries Ic and Is are presented for the reaction gp γ→p→pπ0η. The latter is a feature exclusive to the acoplanar kinematics of multi‐meson final states and has been measured for the first time.