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

Abstract

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 γp→ρ+n and γn→ρ−p processes without model-dependences except for the magnetic moment μρ±=±2.01 and electric quadrupole moment Qρ±=±0.027 fm2 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