Coupling hadron-hadron thresholds within a chiral quark model approach

TL;DR

This paper reviews how incorporating hadron-hadron threshold couplings into the chiral quark model improves understanding of heavy meson spectroscopy, especially for states like X(3872) with complex properties.

Contribution

It demonstrates the extension of the naive quark model by coupling to two-meson states within the chiral quark framework, highlighting its relevance for heavy meson states.

Findings

Threshold coupling explains the properties of X(3872)

Improved mass predictions for heavy mesons

Enhanced understanding of decay properties

Abstract

Heavy hadron spectroscopy was well understood within the naive quark model until the end of the past century. However, in 2003, the $X(3872)$ was discovered, with puzzling properties difficult to understand in the simple naive quark model picture. This state made clear that excited states of heavy mesons should be coupled to two-meson states in order to understand not only the masses but, in some cases, unexpected decay properties. In this work we will review how the naive quark model can be complemented with the coupling to two hadron thresholds. This program has been already applied to the heavy meson spectrum with the chiral quark model and we show some examples where thresholds are of special relevance.