High statistics study of the reaction $\gamma p\to p\pi^0\eta$

Abstract

Photoproduction off protons of the $p\pi^0\eta$ 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 $\pi^0\eta$ 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 $\Sigma$, $I^{s}$ and $I^{c}$, the latter two characterize beam asymmetries in case of three-body final states. $\Delta(1232)\eta$, $N(1535){1/2^-}\pi$, and $p a_0(980)$ are the dominant isobars contributing to the reaction. The partial wave analysis confirms the existence of some nucleon and $\Delta$ resonances for which so far only fair evidence was reported. A large number of decay modes of known nucleon and $\Delta$ resonances is presented. It is shown that detailed investigations of decay branching ratios may provide a key to unravelling the structure of nucleon and $\Delta$ resonances.