Constraints on the proton's gluon distribution from prompt photon production

We analyze the capability of prompt proton production in pp and pp-bar collisions to constrain the gluon distribution of the proton, considering data from fixed-target experiments as well as collider measurements. Combined fits are performed to these large-pT direct-γ cross sections and lepton-proton deep-inelastic scattering data in the framework of next to-leading order perturbative QCD. Special attention is paid to theoretical uncertainties originating from the scale dependence of the results and from the fragmentation contribution to the prompt photon cross section. (Author)