摘要
Although Quantum chromodynamics(QCD)has been accepted as the fundamental theory for strong interaction,it remains a curious fact and a longstanding puzzle that strong interaction exhibits distinct pictures at different energy regimes:at high energy the particles behave as bound states consisting of quarks and gluons(partons)interacting through the fundamental QCD interactions,whereas at low energy protons and neutrons(nucleons)become the relevant degrees of freedom and they interact via the effective nucleon-nucleon interactions.
