The strong nuclear interaction

• Characteristics:

  • “Asymptotic freedom”: At short distances (high energies), it decreases logarithmically: quarks & gluons are weakly coupled.
  • Confinement: At large distances, it becomes very strong. Quarks do not occur isolated in nature but only in hadronic (colorless) bound-states as mesons (qq) and baryons (qqq) !
  • Chiral symmetry breaking: “Constituent” quarks acquire dynamically a mass in a confined medium:
    • “Current” mq (5-10 MeV) << “Constituent” mq (300 MeV)
  • Non-zero “QCD vacuum”: Vacuum filled with quark-antiquark virtual pairs (and gluon pairs):
    • quark condensate: <>  (235 MeV)3
    • gluon condensate: < sGG>  (500 MeV)4

Notes: