Muon Collaboration: J.G. Ashman, B. Badelek, G. Baum, J. Beaufays, et al., "An investigation of the spin structure of the proton in deep inelastic scattering of polarised muons on polarised protons," Nuclear Physics B, 328:1-35, 1989.
J.G. Ashman (University of Sheffield, England): "In the past 20 years many experiments have studied the structure of the nucleon via deep inelastic scattering of charged leptons and neutrinos from unpolarized targets. This has led to the confirmation of the quark parton model, which states that the nucleon is composed of three valence quarks that give the overall properties of the nucleon, and a `sea' of virtual quark pairs. The model has also successfully explained static spin phenomena, such as the ratio of the neutron to proton magnetic moments, by hypothesizing that the spin of the nucleon is due entirely to the valence quarks.
"However, direct information on how the spin of the nucleon ...
