Quark Models and Quark Phenomenology

TL;DR

This paper reviews the development of quark models and phenomenology, highlighting their success in explaining hadron spectra, quantum numbers, and relations, predating and contributing to the foundation of QCD.

Contribution

It provides a comprehensive overview of early quark models, their predictions, and how they laid the groundwork for the development of Quantum Chromodynamics.

Findings

Quark models accurately predicted hadron quantum numbers.

The models explained meson and baryon spectra systematically.

They predicted relations between masses and reaction cross sections.

Abstract

Overwhelming experimental evidence for quarks as real physical constituents of hadrons along with the QCD analogs of the Balmer Formula, Bohr Atom and Schroedinger Equation already existed in 1966. A model of colored quarks interacting with a one-gluon-exchange potential explained the systematics of the meson and baryon spectrum and gave a hadron mass formula in surprising agreement with experiment. The simple quark model dismissed as heresy and witchcraft by the establishment predicted quantum numbers of an enormous number of hadronic states as well as relations between masses, reaction cross sections and electromagnetic properties, all unexplained by other approaches. Further developments leading to QCD included confinement in the large $N_c$ limit, duality, dual resonance and string models, high energy scattering systematics, unified treatment of mesons and baryons, no exotics and no free quarks.