Photoproduction of $\phi$-meson on protons was studied by means of linearly polarized photons at forward angles in the low-energy region from threshold to $E_{ \gamma}$= 2.37 GeV. The differential cross sections at $t = -|t|_{ min}$ do not increase smoothly as $E_{ \gamma}$ increases, but show a local maximum at around 2.0 GeV. The angular distributions demonstrate that $\phi$-mesons are photo-produced predominantly by helicity-conserving processes, and the local maximum is not likely due to unnatural-parity processes.
Categories: nucl-ex