Differential cross sections for coherent and incoherent neutral-pion photoproduction from calcium.

Differential and absolute cross sections for the coherent reaction /sup 40/Ca(/gamma/,/pi//sup 0/)/sup 40/Ca g.s., as well as for the incoherent reaction /sup 40/Ca(/gamma/,/pi//sup 0/)/sup 40/Ca(g.s.), have been measured with monochromatic photons in the threshold region (/ital E//sub /gamma//=157--169 MeV). The differential cross section for the coherent process exhibits a diffraction minimum due to the nuclear mass form factor while the incoherent cross section is rather structureless. The cross sections are in good agreement with recent distorted-wave impulse-approximation calculations.