Heavy mesons in the Quark Model

TL;DR

This paper reviews the quark model's success in describing heavy mesons and discusses recent discoveries of states that challenge the naive model, suggesting more complex structures like meson-meson molecules.

Contribution

It provides an overview of heavy meson spectroscopy and highlights the need to consider higher Fock components and molecular structures beyond the naive quark model.

Findings

The quark model successfully describes many heavy mesons.

Recent discoveries like X(3872) challenge the naive quark model.

Some heavy mesons may be meson-meson molecules.

Abstract

Since the discovery of the $J/\psi$, the quark model was very successful in describing the spectrum and properties of heavy mesons including only $q\bar q$ components. However since 2003, with the discovery of the $X(3872)$, many states that can not be accommodated on the naive quark model have been discovered, and they made unavoidable to include higher Fock components on the heavy meson states. We will give an overview of the success of the quark model for heavy mesons and point some of the states that are likely to be more complicated structures such as meson-meson molecules.