We suggest that the γp→ϕηp reaction cross section, in the
kinematics where the ηp invariant mass in the final state lies between
the threshold value (mp​+mη​) and the N*(1535) resonance mass, is
largely determined by the ηN scattering amplitude close to threshold. The
initial photon energy is chosen in the range 4<EγLab​<5 GeV, in
order to reach low (absolute) values of the squared 4-momentum transfer from
the initial photon to the final Ï•-meson. In these conditions, we expect
the t-channel π0- and η-meson exchanges to drive the dynamics
underlying the γp→ϕηp process. We show that the
η-exchange is the dominating contribution to the cross section while the
π0-exchange is negligible. The η-π0 interference is of the order
of 20−30. The sign of this term is not known and alters significantly our
results. Data on the γp→ϕηp process would be therefore very
useful to help unravelling the behavior of the ηp scattering amplitude
close to threshold and assessing the possibility of producing η-nucleus
bound states.Comment: 8 pages, 6 figures, Invited talk at MESON 2006, June 9th-13th, 2006,
Cracow (Poland