All Heavy Tetraquarks: The Dynamical Diquark Model and Other Approaches

TL;DR

This paper reviews various theoretical approaches, including the dynamical diquark model, to interpret the newly observed $X(6900)$ tetraquark state in the di-$J/$ spectrum, and suggests experiments to differentiate these models.

Contribution

It provides a comprehensive survey of existing theories, highlights the dynamical diquark model's perspective, and proposes experimental tests to distinguish between competing interpretations.

Findings

Interpretation of $X(6900)$ as a tetraquark state

Comparison of different theoretical models

Proposals for experimental discrimination

Abstract

The 2020 announcement by LHCb of a narrow structure $X(6900)$ in the di-$J/\psi$ spectrum -- a potential $c\bar c c\bar c$ state -- has opened a new era in hadronic spectroscopy. In this talk, we briefly survey theory works preceding this event, examine key features of the observed spectrum, and then discuss how subsequent theory studies (including with the author's own dynamical diquark model) have interpreted these features. We conclude with proposals for experiments capable of distinguishing competing interpretations.