Evidence for a narrow structure at W similar to 1.68 GeV in eta photoproduction off the neutron

New results on quasi-free eta photoproduction on the neutron and proton bound in a deuteron target are presented. The gamma n -> eta n quasi-free cross section reveals a bump-like structure which is not seen in the cross section on the proton. This structure may signal the existence of a relatively narrow (M similar to 1.68 GeV, Gamma <= 30 MeV) baryon state. (c) 2007 Elsevier B.V. All rights reserved.