We report exclusive measurements for the η photoproduction on a proton target. The differential cross sections and photon beam asymmetries of the γp→ηp reaction are measured in a center-of-mass energy (W) range of 1.82-2.32 GeV and a polar angle range of -1.0<cosθc.m.η<0.6 by using a large acceptance calorimeter (BGOegg) and forward-angle charged-particle detectors at the SPring-8 LEPS2 beamline. The reaction is identified with a kinematic fitting method to select a recoil proton and two photons produced in an η meson decay. A bump structure at W = 2.0-2.3 GeV in the differential cross section is confirmed at extremely backward η polar angles, where the existing data are inconsistent with each other. This bump structure is likely associated with high-spin resonances that couple with ss¯ quarks. The photon beam asymmetries in a wide η polar angle range for the photon beam energies above 2.1 GeV are reported for the first time, providing an additional constraint to nucleon resonance studies at high energies.
ASJC Scopus subject areas
- Nuclear and High Energy Physics