Parton Densitites at High-x

Abstract

Reliable knowledge of parton distributions at large x is crucial for many searches for new physics signals in the next generation of collider experiments. Although these are generally well determined in the small and medium x range, it has been shown that their uncertainty grows rapidly for x>0.1. We examine the status of the distributions in light of new questions that have been raised about "large-x" parton distributions, as well as recent measurements which have improved the parton uncertainties.