Eta photoproduction as a test of the extended chiral symmetry

Abstract

We analyze the γp→ηp process from threshold up to 1.2 GeV, employing an effective Lagrangian approach that allows for a mixing of eta couplings of pseudoscalar and pseudovector nature. The mixing ratio of the couplings may serve as a quantitative estimation of the SUL(3)×SUR(3) extended chiral symmetry violation in this energy regime. The data analyzed (differential cross sections and asymmetries) show a preference for the pseudoscalar coupling—91% of pseudoscalar coupling component for the best fit. We stress that a more conclusive answer to this question requires a more complete electromagnetic multipole database than the presently available one.