Data are presented on the details of the interaction $\gamma +p\to p+{\rho }^0$ observed in a 12-in. hydrogen bubble chamber exposed to a bremsstrahlung photon beam of 6-BeV maximum energy at the Cambridge Electron Accelerator. The energy dependence of the cross sections, the production angular distributions, and the decay angular distributions of the ${\rho }^0\text{'}\mathrm{s}$ are compared with the predictions of the one-pion-exchange (OPE) mechanism and with a diffraction or multiperipheral model proposed by Berman and Drell. These data, as well as a comparison with ${\omega }^0$ and with ${\rho }^0+N^{*}\mathrm{}\left(1238\right)\mathrm{}$ production, reject the OPE model and favor a diffraction mechanism.

• Received 22 December 1965

DOI:https://doi.org/10.1103/PhysRev.146.994