COHERENT ETA PHOTOPRODUCTION ON HE-4 AND C-12 IN THE NEAR-THRESHOLD REGION

摘要

Coherent eta meson photoproduction on He-4 and C-12 is considered in the near-threshold region. The elementary eta photoproduction operator includes contributions from the S-11(1535) and D-13(1520) resonances as well as t-channel vector meson exchange and the nucleon pole terms. Due to the suppression of the dominant S-11(1535) resonance for spin and isospin saturated nuclei, the reaction is mainly governed by omega exchange. Furthermore, the influence of Fermi motion and of different prescriptions for the choice of the invariant reaction energy W-gamma N in the elementary amplitude is studied. (C) 1997 Elsevier Science B.V. [References: 30]