  Recent analysis of proton and deuteron deep-inelastic scattering data have
suggested that the extracted d/u quark distribution ratio at large x may be
significantly larger than previously believed, if the data are corrected for
nuclear binding effects in the deuteron. We examine the sensitivity to the
large-x d/u ratio of lepton asymmetries from W-boson production in p-pbar and
p-p collisions at large rapidity, which do not suffer from nuclear
contamination.
