Prof. Emer. Dr. Mitja Rosina (FMF): Mesonic molecules
Several constituent quark models agree more or less in the descripton of baryons and mesons. They may, however, largely disagree in their predictions for two-meson molecules (tetraquarks). So far, a number of resonances have been found and studied with various success. A good benchmark of of our understanding of quark models are, however, bound states of two heavy mesons, and a search for them is continuing. In 2004 we predicted (Janc & Rosina) a weakly bound state of two heavy mesons, D+D*. It is a great satisfaction that it has been finally detected and confirmed after 17 years in CERN in July 2021. In the present Colloquium, I shall describe some of its salient features.