Photoproduction of the ηπ0 System off a Proton Target at Eγ = 8.5 GeV

The $\eta \pi$ decay channel is one of the "golden channels'' to search for the $\pi_1$ and other spin-exotic mesons. These exotic states show up as odd partial waves in the decay of the $\eta\pi$ system. Searching for this resonance requires a detailed understanding of the nearby $a_2(1320)$ meson and necessitates a characterization of the double Reggeon exchange process that can mimic exotic signatures. The first measurement of the differential photoproduction cross section, $d\sigma/dt$, of the $a_2(1320)$ meson at photon beam energies of $8.2-8.8$\,GeV and in the four-momentum transfer range of 0.1 to 1.0\,GeV$^2$ is performed. A full partial wave analysis is performed in the $\eta\pi^0$ invariant mass region around 1.3\,GeV$/c^2$ using amplitudes that depend on the polarization of the incoming photon beam, which allows us to separate the contributions of natural and unnatural parity exchange to the differential cross section. The partial wave analysis suggests that the $a_2(1320)$ is produced predominantly through natural exchange with total cross-section [WAITING FOR RESULT] over the measured interval. Additionally, an analysis will be presented of the $\gamma p \to \eta \pi^0 p$ reaction beyond the resonance region, ($M(\eta\pi) > 1.6$~GeV). As input for the development of models to describe polarized photoproduction in this mass range at GlueX energies, we measure the $\Sigma$ beam asymmetry for individual $\eta$ and $\pi$ mesons for the above reaction, $\Sigma_\eta$ and $\Sigma_\pi$, as functions of several kinematic variables. These results suggest that baryon production can contribute significantly to the asymmetries. A comparison is made to measurements from $\gamma p \to \eta \pi^-\Delta^{++}$.