Nondiffractive feature of γN → ρ ± N with ρ -meson electromagnetic multipole moments

We investigate photoproduction of charged ρ off the nucleon using ρ ( 770 ) + π ( 140 ) Regge pole exchanges by considering the ρ -meson electromagnetic multipole moments. The significance of the Ward identity at the γρρ vertex is emphasized for current conservation in the process. Given π exchange with the well-known coupling constants for γπρ and πNN , we analyze the role of the ρ exchange in the γ p → ρ + n and γ n → ρ − p processes without model-dependences except for the magnetic moment μ ρ ± = ± 2.01 and electric quadrupole moment Q ρ ± = ± 0.027 fm 2 taken from theoretical estimates. The nondiffractive feature of both cross sections is reproduced with a rapid decrease beyond the resonance region by the dominance of π exchange over the ρ . Cross sections for differential and density matrix elements are presented to compare with existing data. The parity and photon polarization asymmetries are predicted to demonstrate the apparent roles of the ρ -meson electromagnetic multipole moments.