Quark model: recent issues

TL;DR

This paper reviews recent challenges and developments in constituent quark models, including exotic hadronic states and the application of the $1/N_c$ expansion approach to support quark model dynamics.

Contribution

It provides a survey of recent issues in quark models and demonstrates the effectiveness of the $1/N_c$ expansion in describing baryon properties.

Findings

Higher Fock components influence baryon wave functions

Open charm and charmonium-like states may be tetraquarks

The $1/N_c$ expansion supports quark model dynamics

Abstract

In the first part I briefly survey recent issues in constituent quark models raised by the observation of unusual hadronic states. In particular I discuss the role of higher Fock components in the wave function of baryons and the possible interpretation of open charm and of new charmonium-type resonances as tetraquarks. In the second part I show support for the quark model dynamics obtained in a model independent way from the $1/N_c$ expansion approach of QCD which proved to be successful in describing baryon properties.