Quantum Chromodynamics and Particle Interactions

Quantum chromodynamics is the theory governing the strong nuclear force, describing how quarks and gluons bind together to form the protons, neutrons, and more exotic particles that make up nearly all visible matter. Because the strong force becomes so intense at low energies that quarks are permanently confined inside composite particles called hadrons, extracting precise predictions requires specialized tools — among them lattice QCD, which discretizes spacetime to perform numerical calculations, and renormalization group methods, which systematically handle the way physical quantities change across energy scales. A central puzzle is understanding the full spectrum of hadrons: conventional mesons and baryons are relatively well characterized, but experiments have uncovered states like certain charmonium resonances that don't fit neatly into the standard quark-model picture, suggesting more complex internal structures involving extra quark-antiquark pairs or gluonic degrees of freedom. Pinning down the internal momentum structure of the proton through parton distribution functions, and explaining the infrared behavior of QCD's fundamental propagators, remain active areas where theory and high-energy experiments are still working toward a coherent account.

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Keywords

QCDcharmoniummesonsbaryonsparton distributionsrenormalization group