Exotic hadrons

Exotic hadrons are subatomic particles made of quarks and bound by the strong interaction that are not predicted by the simple quark model. That is, they do not have the same quark content as ordinary hadrons: exotic baryons have more than just the three quarks of ordinary baryons, and exotic mesons do not have one quark and one antiquark like ordinary mesons.

Types of exotic hadrons include glueballs, hadrons consisting entirely of gluons.