The XYZ-states - a new particle zoo?
Dr. Christoph Hanhart (FZ Jülich)

Even after several decades of intense research the strong sector of QCD is still not fully understood. For a long time there was a strong believe that it would be a lot easier to analyze the sector of heavy quarks, since asymptotic freedom allows for at least some perturbative treatment of those systems. And indeed the quark model celebrated a large number of successes in describing the low lying charmonium and bottomonium states. However, since 10 years a large number of states baptized either X, Y, or Z were discovered that neither in the mass and width nor in their decay properties seem to fit into the quark model.
With the recent discoveries of charged states in the heavy quarkonium mass range it became clear: our picture about the structure of hadrons needs to be extended.

In the talk I will briefly review the properties of the quark model and then focus on theoretical ideas that try to accomodate the mentioned exciting discoveries.
Especially I will discuss how it could be possible in the future to (hopefully) get a theoretical understanding of this new particle zoo.