Beam asymmetry Σ for the photoproduction of η and η ′ mesons at E γ = 8.8 GeV

Abstract

© 2019 American Physical Society. We report on the measurement of the beam asymmetry ς for the reactions γ - p→pη and γ - p→pη′ from the GlueX experiment using an 8.2-8.8-GeV linearly polarized tagged photon beam incident on a liquid hydrogen target in Hall D at Jefferson Laboratory. These measurements are made as a function of momentum transfer -t with significantly higher statistical precision than our earlier η measurements and are the first measurements of η′ in this energy range. We compare the results to theoretical predictions based on t-channel quasiparticle exchange. We also compare the ratio of ςη to ςη′ to these models as this ratio is predicted to be sensitive to the amount of ss exchange in the production. We find that photoproduction of both η and η′ is dominated by natural parity exchange with little dependence on -t.