An introduction to the quark model Jean-Marc Richard Université de Lyon & Institut de Physique Nucléaire de Lyon IN2P3-CNRS & UCB, 4 rue Enrico Fermi, 69622 Villeurbanne, France
[email protected] May 25, 2012 Abstract This document contains a review on the quark model, prepared for lectures at the Niccolò Cabeo School at Ferrara in May 2012. It includes some historical aspects, the spectral properties of the 2-body and 3-body Schrödinger operators applied to mesons and baryons, the link between meson and baryon spectra, the role of flavour independence, and the speculations about stable or metastable multiquarks. The analogies between few-charge systems and few-quark bound states will be under- lined. Contents 1 Prelude: few charge systems in atomic physics 3 1.1 Introduction . .3 1.2 The atomic two-body problem . .3 1.3 Three-unit-charge ions . .5 arXiv:1205.4326v2 [hep-ph] 24 May 2012 1.4 Three-body exotic ions . .5 1.5 Molecules with four unit charges . .6 2 A brief historical survey 7 2.1 Prehistory . .7 2.2 Early hadrons . .7 2.3 Generalised isospin . .9 2.4 The success of the eightfold way . 10 2.5 The fundamental representation: quarks . 10 2.6 The OZI rule . 12 2.7 First quark models . 13 2.8 Heavy quarks . 14 2.9 Confirmation . 15 1 2 AN INTRODUCTION TO THE QUARK MODEL 3 The quark–antiquark model of mesons 16 3.1 Introduction . 16 3.2 Quantum numbers . 16 3.3 Spin averaged spectrum . 17 3.4 Improvements to the potential .