ABSTRACT
In Quantum Chromodynamics (QCD) framework, the three quarks in a spin 12 baryon are treated as massless and point-like particles. These are denominated as current quarks. In contrast, at low energies theoretical consistency demands that the quarks be treated as possessing a finite size (i.e., be non-point-like structure) and a finite mass (about 300 MeV). These are then termed as constituent quarks. Experimentally, current quarks are studied in deep inelastic scattering, and are specified by quantum numbers such as electric charge, baryon number, weak hypercharge numbers and isospin. Hence these are the quarks which arise in the Standard Model of particle physics. As per these unpolarized structure functions one does not perceive any difference between the quasi-quarks and the constituent-quarks. Experiments have been completed with longitudinally polarized electron and muon beams on longitudinally polarized hydrogen and deuterium targets.
