From Heavy Quarkonia to Double Charm/Beauty Tetraquarks

GSI-FAIR/PANDA Colloquium

Introducing quarks to describe the known mesons and baryons, Murray Gell-Mann, in 1964, suggested the existence of further qqqq mesons (tetraquarks) and qqqqq baryons (pentaquarks).
In 1977, R. Jaffe proposed a model of the lightest scalar mesons as diquark-antidiquark pairs and A. de Rujula, H. Georgi and S. Glashow coined the term hadron molecules, to describe hadrons made by meson-antimeson pairs bound by the familiar nuclear forces, also an overall four-quark system. The two alternative pictures have been employed to interpret an unexpected hadron discovered by BELLE in 2003, the X(3872), confirmed by BABAR and seen in many other High Energy experiments. Since then, a wealth of Exotic Hadrons have been observed, mesons and baryons that cannot be described by the classical Gell-Mann, qq and qqq, configurations.
In the Colloquium, I try to illustrate this new chapter of Particle Spectroscopy with a selection of results on the structure and symmetry pattern of the Exotic Hadrons, recent experimental discoveries and future perspectives.

Medical masks are required in the lecture hall!