Nucleon spin structure at very high x

Dyson-Schwinger equation treatments of the strong interaction show that the presence and importance of nonpointlike diquark correlations within the nucleon are a natural consequence o f dynamical chiral symmetry breaking. Using this foundation, we deduce a collection of simple formulae, expressed in terms of diquark appearance and mixing probabilities, from which one may compute ratios of longitudinal-spin-dependent u- and d-quark parton distribution functions on the domain x≃ 1. A comparison with predictions from other approaches plus a consideratio n of extant and planned experiments shows that the measurement of nucleon longitudinal spin asymmetries on x≃ 1 can add considerably to our capacity for discriminating be tween contemporary pictures of nucleon structure.