Measurement of the t-dependence for the Beam Asymmetry of Photoproduced η Mesons at GlueX

We report on the photoproduction of η mesons studied at the GlueX experiment at Thomas Jefferson National Laboratory in Newport News, VA. A linearly polarized photon beam at energies between 8.2 and 8.8 GeV, incident on a liquid hydrogen target, produces η dominantly through t-channel exchanges. Azimuthal angular distributions of the η, with respect to the direction of the polarized photon facilitate the extraction of the beam asymmetry Σ for the reaction γp→ηp. We can understand the production mechanisms of the η by analyzing Σ_η, which is sensitive to the particles exchanged. Compared to previous GlueX results [1,2], we have access to five times the statistics, thereby allowing us to extend these measurements to values beyond the previous limitation of -t ≤1.1 (GeV/c)². Preliminary results will be shown for events reconstructed from the decay of η→π⁺π^-π⁰ and η→γγ.

[1] S. Adhikari et al. [GlueX Collaboration], "Beam Asymmetry ∑ for the Photoproduction of η and η' Mesons at E_γ = 8.8 GeV,'' Phys. Rev. C, no. 5, 052201 (2019)

[2] H. Al Ghoul et al. [GlueX],"Measurement of the beam asymmetry ∑ for π⁰ and η  photoproduction on the proton at E_γ = 9 GeV,'' Phys. Rev. C, no.4, 042201 (2017)