Heavy Quark Production at HERA

Heavy quark production in ep scattering predominantly occurs via the process of boson gluon fusion (BGF, see fig.la,e). The cross section is thus directly sensitive to the gluon distribution in the proton. In photoproduction the photon virtualities are small (Q 2 ~ 0), and the photon can reveal a hadronic structure. In a leading order picture, the production process can be divided into direct photon (fig. 1a) or resolved photon (fig.lb-e) processes. In the latter the photon acts as a source of incoming quarks and gluons, and only a fraction of the photon momentum participates in the hard scattering.