ABSTRACT:
It is usually assumed that the structure functions measured in deep
inelastic lepton-proton scattering are the probability distributions
for finding quarks and gluons in the target nucleon. In fact, gluon
exchange between the fast, outgoing partons and the target spectators,
which is usually assumed to be an irrelevant gauge artifact, affects
the leading-twist structure functions in a profound way, leading to
diffractive leptoproduction processes, shadowing of nuclear structure
functions, and target spin asymmetries. In particular, final-state
interactions from gluon exchange leads to single-spin asymmetries in
semi-inclusive deep inelastic lepton-proton scattering which are not
power-law suppressed at large photon virtuality Q^2 at fixed x_{bj}. |