High statistics study of the reaction $γp\to pπ^0η$

Photoproduction off protons of the $pπ^0η$ three-body final state was studied with the Crystal Barrel/TAPS detector at the electron stretcher accelerator ELSA at Bonn for incident energies from the $π^0η$ production threshold up to 2.5\,GeV. Differential cross sections and the total cross section are presented. The use of linearly polarized photons gives access to the polarization observables $Σ$, $I^{s}$ and $I^{c}$, the latter two characterize beam asymmetries in case of three-body final states. $Δ(1232)η$, $N(1535){1/2^-}π$, and $p a_0(980)$ are the dominant isobars contributing to the reaction. The partial wave analysis confirms the existence of some nucleon and $Δ$ resonances for which so far only fair evidence was reported. A large number of decay modes of known nucleon and $Δ$ resonances is presented. It is shown that detailed investigations of decay branching ratios may provide a key to unravelling the structure of nucleon and $Δ$ resonances.

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