Charm Photoproduction

We present results on the photoproduction of 10 000 charmed particles from the ${10}^{8}$ recorded triggers of Fermilab experiment E691. The total cross section for the photoproduction of ${D}^{0}$ and ${D}^{+}$ particles (and antiparticles) for ${x}_{F}>0.2$ is measured to be 3.88\ifmmode\pm\else\textpm\fi{}0.06\ifmmode\pm\else\textpm\fi{}0.40 \ensuremath{\mu}b/Be nucleus at $〈{E}_{\ensuremath{\gamma}}〉=145$ GeV. We have also measured the relative production of different charmed particles, their ${p}_{T}^{2}$ and ${x}_{F}$ distributions, and the energy dependence of the total charm cross section. The mean ${p}_{T}^{2}$ is 1.16\ifmmode\pm\else\textpm\fi{}0.04 Ge${\mathrm{V}}^{2}$/${\mathit{c}}^{2}$ and the ratio of charm cross sections at 200 and 100 GeV is 1.96\ifmmode\pm\else\textpm\fi{}0.24. Results of fits to the ${x}_{F}$ distribution are also reported.