Measurement of the beam asymmetry $\mathrm{\Sigma }$ for ${\pi }^0$ and $\eta$ photoproduction on the proton at $E_{\gamma }=9$ GeV

We report measurements of the photon beam asymmetry $\mathrm{\Sigma }$ for the reactions $\vec{\gamma }p\to p{\pi }^0$ and $\vec{\gamma }p\to p\eta$ from the GlueX experiment using a 9 GeV linearly-polarized, tagged photon beam incident on a liquid hydrogen target in Jefferson Lab’s Hall D. The asymmetries, measured as a function of the proton momentum transfer, possess greater precision than previous ${\pi }^0$ measurements and are the first $\eta$ measurements in this energy regime. The results are compared with theoretical predictions based on $t$-channel, quasi-particle exchange and constrain the axial-vector component of the neutral meson production mechanism in these models.