Quantum chromodynamics

Quantum chromodynamics (QCD) is the quantum field theory of the strong interaction. It describes quarks and gluons interacting through color charge, with gluons also carrying color.

Color charge: A quantum number carried by quarks and gluons that determines their strong-interaction behavior. It is the charge through which QCD couples quarks and gluons.
Quark: An elementary fermion carrying fractional electric charge and color charge. Quarks are the matter fields whose strong interactions QCD describes.
Murray Gell-Mann: A physicist who proposed the quark model and helped develop the classification of hadrons. His quark model supplied the constituents that QCD later made dynamic.
Hadron: A composite particle made of quarks and gluons that experiences the strong interaction. Hadrons are the color-neutral bound states QCD must explain.
Quantum electrodynamics: The quantum field theory of electromagnetic interactions between electrically charged particles. Unlike photons, gluons carry the charge of their own interaction and self-interact.
Gluon: A massless gauge boson of the strong interaction that carries color charge. Gluons mediate the force and interact with one another because they carry color.
SU(3): A group of unitary transformations in three complex dimensions with determinant one. QCD’s color symmetry is based on the gauge group SU(3).
George Zweig: A physicist who independently proposed a constituent model of hadrons using particles he called aces. His parallel proposal helped establish the quark picture underlying QCD.
Proton: A stable baryon containing two up quarks and one down quark, with additional quark–gluon structure. Its mass and internal structure emerge largely from QCD dynamics.
Electroweak interaction: The unified description of electromagnetic and weak interactions at high energies. Its gauge bosons differ from QCD gluons in charges and interaction structure.

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