Constraints on the Up-Quark Valence Distribution in the Proton.

The high-x data from the ZEUS Collaboration are used to extract parton density distributions of the proton deep in the perturbative regime of QCD. The data primarily constrain the up-quark valence distribution and new results are presented on its x dependence as well as on the momentum carried by the up quark. The results were obtained using Bayesian analysis methods which can serve as a model for future parton density extractions.