High-Energyπ0Photoproduction from Hydrogen with Unpolarized and Linearly Polarized Photons

We have completed measurements of the differential cross section for $\gamma +p\to {\pi }^0+p$, and the asymmetry with polarized photons, for incident photon energies from 4 to 18 GeV and momentum transfers between $t=-0.1\mathrm{} \mathrm{and} -1.4\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. The experiment was performed at the Stanford Linear Accelerator Center, using the SLAC 1.6-GeV/c spectrometer to analyze protons recoiling from a hydrogen target. For the cross-section measurements a normal collimated bremsstrahlung beam was used. For the asymmetry measurements the polarized photons were produced by coherent bremsstrahlung from a diamond crystal, and a coincidence was required between the recoil proton and one of the ${\pi }^0$ decay photons in a shower counter.