All Heavy Tetraquarks:The Dynamical Diquark Model and Other Approaches

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