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 $\Sigma$ for the reaction $\vec\gamma p \rightarrow \eta p $. 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→γγ and η→π⁺π^-π⁰.

 [1] S.~Adhikari et al. [GlueX Collaboration]Phys. Rev.  C {100}, no. 5, 052201 (2019) doi:10.1103/PhysRevC.100.052201

[2] H.~Al Ghoul et al. [GlueX],Phys. Rev. C 95, no.4, 042201 (2017)

doi:10.1103/PhysRevC.95.042201

[arXiv:1701.08123 [nucl-ex]].