Speaker
Description
Nucleon valence quark structure at very high values of the scaling variable $x$ is sensitive to the mechanism of SU(6) breaking. In particular the valence quark polarizations $\Delta u/u$ and $\Delta d/d$ can be predicted by quark models, perturbative QCD, and other approaches, with significantly different expected
results. Present data are not sufficiently precise in the high-$x$ region to stringently test these predictions. New experiments at Jefferson Lab with 12 GeV beam will significantly improve our knowledge of these quantities out to $x \approx 0.8$, albeit with significant remaining sensitivity to models and assumptions used in their extraction from experimental results. In my talk, I will lay out the present situation and expected results for the 12 GeV program, and address the question what improvements we can expect from a higher luminosity, 24 GeV electron beam at Jefferson Lab.
