Nuclear Physics Seminars

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}.