Quark model

The quark model classifies hadrons as combinations of quarks and antiquarks. It accounts for their patterns of charge, spin, strangeness, and other quantum numbers.

Quark: An elementary fermion that carries color charge and combines with other quarks to form hadrons. Quarks are the model’s constituents, distinguished by flavor and quantum numbers.
Baryon: A hadron composed primarily of three quarks, including protons and neutrons. Three-quark combinations produce the baryon families classified by the model.
Murray Gell-Mann: An American physicist who proposed the quark model and developed the Eightfold Way. Gell-Mann named quarks and used them to explain hadron multiplets.
Proton: A positively charged baryon with valence-quark content uud. Its charge and quantum numbers follow from its valence-quark assignment.
Quantum chromodynamics: The quantum field theory of quarks, gluons, and the strong interaction. Unlike the classification model, QCD supplies the fundamental dynamics binding quarks into hadrons.
Antiquark: The antiparticle of a quark, with opposite electric charge and other additive quantum numbers. Antiquarks pair with quarks to form mesons in the model.
Meson: A hadron composed primarily of a quark and an antiquark. Quark–antiquark combinations account for meson families and their quantum numbers.
George Zweig: A physicist who independently proposed constituent particles called aces to account for hadron patterns. Zweig’s 1964 scheme reached a constituent picture independently of Gell-Mann’s.
Neutron: A neutral baryon with valence-quark content udd. Comparing it with the proton tests how changing one constituent changes hadron properties.
Constituent quark model: A phenomenological model that treats hadrons as bound states of quarks with effective masses. It adds dynamical assumptions to the quark model’s basic classification scheme.

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