Mass creation by the strong interaction: Glueballs -- status and perspectives

Glueballs represent a fascinating aspect of the strong interaction in nature. Gluons that serve as the mediators of the strong interaction are massless particles, but they possess a property unique to the strong interaction called color charge, which is analogous to electric charge in the electromagnetic interaction. Glueballs are composed of multiple gluons and would be massless without color charges. The interaction of the color charges, however, makes glueballs becoming massive objects. Glueballs thus offer a unique way to study the mass creation of strongly interacting particles.