Photoproduction of Vector Mesons andΔ(1238)in Hydrogen and Deuterium and theρπγWidth

Abstract

In a study of the photoproduction reactions $\gamma p\to {\rho }^{-}{\Delta }^{++}$ and $\gamma n\to {\omega }^0{\Delta }^0$ at 4.3 GeV, we obtain a substantial cross section, 1.8±0.4 μb, for the first reaction and an upper limit of 0.5 μb for the second. If one-pion exchange dominates the above reactions, then by SU(3) one predicts ${\omega }^0{\Delta }^0:{\rho }^{-}{\Delta }^{++}=2:1\mathrm{}$. We believe that the discrepancy between theory and experiment is due to exchanges other than $\pi$ mesons contributing to charged $\rho$ photoproduction, thus making the derivation of $\Gamma \left(\rho \pi \gamma \right)$ from it rather unreliable.