Study of charm production mechanisms at the Fermilab Tagged Photon Spectrometer: γBe → DantiD x and γA → Ψx

This paper describes recent work on charm photoproduction mechanisms based on data from Experiment 691 at the Fermilab Tagged Photon Spectrometer. Preliminary results on open charm production in the energy range 80-190 GeV are reported based on a preliminary analysis of 3000 charm events, comprising 30% of the data sample. These results include fits to transverse momentum and XF distributions, a measurement of the total charm production cross section on Be and its increase with energy from 100 to 200 GeV, as well as a measurement of the relative fraction of antiD, D, and D* production. Also reported is data based on a special closed geometry run to study the A dependence of Ψ photoproduction. For the first time in a single experiment, relative cross sections on H, Be, Fe and Pb for both the coherent and incoherent components of the signal have been measured with reduced systematic errors and these results are reported here