Tetraquarks in the 1/N expansion and meson-meson resonances

TL;DR

This paper explores the role of diquarks and the 1/N expansion in describing tetraquark states and meson-meson resonances, revealing narrower resonances and a state counting rule related to meson thresholds.

Contribution

It introduces a diquark-based framework within the 1/N expansion to model tetraquarks and explains their narrow widths and state counting near meson thresholds.

Findings

Tetraquark poles are described using diquarks in meson-meson amplitudes.

Resonances are narrower than previously estimated.

A halving rule for state counting near thresholds is proposed.

Abstract

Diquarks are found to have the right degrees of freedom to describe the tetraquark poles in hidden-charm to open-charm meson-meson amplitudes. Compact tetraquarks result as intermediate states in non-planar diagrams of the 1/N expansion and the corresponding resonances are narrower than what estimated before. The proximity of tetraquarks to meson-thresholds has an apparent role in this analysis and, in the language of meson molecules, an halving rule in the counting of states is obtained.