Elastic Photoproduction ofπ0Mesons from Deuterium

The average differential cross section for the reaction $\gamma +d={\pi }^0+d$ has been measured for photons between 250 and 300 Mev at four angles. A difference measurement with deutero-paraffin and normal paraffin targets was employed. The recoil deuterons were detected by a counter telescope which discriminated against protons by recording the product of the energy and the specific ionization loss of the particles. The reaction was further identified by demanding a coincidence between the deuteron pulse and a pulse from a photon counter placed at an angle corresponding to the direction of the ${\pi }^0$. The values of the differential cross section for various angles of the ${\pi }^0$ in the laboratory system are as follows: The stated errors are the standard statistical errors and apply to the relative cross sections at the various angles. The absolute cross-section scale is subject to an experimental error of 25 percent. The measured cross sections are in agreement with theoretical calculations based on the impulse approximation, with the assumption of equal amplitudes for ${\pi }^0$ production from the proton and neutron and constructive interference.