Results are presented on a series of measurements of $\rho$-photoproduction from hydrogen, deuterium, and complex nuclei ranging up to lead, at photon energies ranging from 4 to 9 GeV. Detailed dipion mass-spectrum fits are presented, using a Drell-type nonresonant background and its interference with the resonant amplitude, with no other arbitrary backgrounds. For hydrogen and deuterium, the inelastic contributions have been subtracted. The $A$ dependence of the cross sections is analyzed to yield values of $\frac{\gamma _{\rho }^{}{}_{}{}^2}{4\pi }$ and ${\sigma }_{\rho N}$ at average photon energies of 6.1, 6.5, and 8.8 GeV. The hydrogen-to-deuterium ratios indicate the presence of possible nondiffractive amplitudes at low energies which then decrease with energy.

• Received 27 May 1971

DOI:https://doi.org/10.1103/PhysRevD.4.2683