π0Photoproduction from Neutrons

We have measured the ratio of the cross section for $\gamma +n\to {\pi }^0+n$ to the cross section for $\gamma +p\to {\pi }^0+p$ at 4.7 and 8.2 GeV. The measurements were made by detecting the recoil nucleons in coincidence with the decay $\gamma$ rays of the ${\pi }^0$'s produced from a deuterium target. At 4.7 GeV the cross-section ratio, $R\equiv \frac{\sigma (\gamma +n\to {\pi }^0+n)}{\sigma (\gamma +p\to {\pi }^0+p)}$, is less than 1.0 at low $t$, with an indication of a dip at about $t=-0.7\mathrm{}{\left(\frac{\mathrm{GeV}}{c}\right)}^2$, and rises to 1.0 at high $t$. The ratios at the higher energy have less structure and are uniformly closer to 1.0.