stronginteraction

Strong interaction, also known as the strong nuclear force, is one of the four fundamental forces of nature. It is described by quantum chromodynamics (QCD), the theory of quarks and gluons, and is responsible for binding quarks into protons, neutrons and other hadrons, and for binding hadrons together in atomic nuclei.

Quarks carry color charge and interact by exchanging gluons, which themselves carry color. The strong interaction is a non-Abelian gauge theory with SU(3) symmetry. Gluons couple to color charge, leading to phenomena such as confinement, whereby quarks and gluons are not observed in isolation, and asymptotic freedom, in which the interaction becomes weaker at high energies or short distances. The strength of the interaction is described by a running coupling constant, alpha_s, which decreases with energy scale.

Range and effective force: The force is short-ranged at the level of individual hadrons, about 1 femtometer. Within nucleons, it is strong; between nucleons, a residual interaction is observed, mediated effectively by meson exchange, producing the nuclear binding.

Phenomena: Deep inelastic scattering reveals quark and gluon substructure; jets in high-energy collisions reflect quark/gluon fragmentation; lattice QCD provides nonperturbative calculations of hadron masses and interactions; quark-gluon plasma is studied in heavy-ion collisions.

Conclusion: The strong interaction explains the majority of visible mass via QCD; it is essential for the stability of matter and plays a central role in cosmology and astrophysics.