Elastic Photoproduction ofπ0Mesons from Deuterium at 270 Mev

The cross section for the process $\gamma +d\to {\pi }^0+d$ has been measured by observing the recoil deuteron. The recoil was first analyzed by a uniform magnetic field and then allowed to pass through a nuclear emulsion. The following values were obtained for the absolute cross section for ${\pi }^0$ production at a photon energy of 270 Mev and ${\pi }^0$ laboratory angles 124° and 168°: $\frac{d\sigma }{d\Omega }\left(124\mathrm{}°\right)=3.2\mathrm{}\pm 0.9$ μb/steradian and $\frac{d\sigma }{d\Omega }\left(168\mathrm{}°\right)=1.3\mathrm{}\pm 0.5$ μb/steradian. The fact that the cross section is the same order of magnitude as the cross section for the production of ${\pi }^0\text{'}\mathrm{s}$ from hydrogen is evidence that constructive interference exists between the ${\pi }^0$ production from the proton and the ${\pi }^0$ production from the neutron. On the basis of approximate theories of meson production from deuterium, a lower limit is deduced for the isotropic part of the angular distribution of ${\pi }^0\text{'}\mathrm{s}$ photoproduced from hydrogen.