In particle physics, a glueball is a hypothetical composite particle. It consists solely of gluon particles, without valence quarks. Such a state is possible because gluons carry color charge and experience the strong interaction. Glueballs are extremely difficult to identify in particle accelerators, because they mix with ordinary meson states.
Theoretical calculations show that glueballs should exist at energy ranges accessible with current collider technology. However, due to the aforementioned difficulty, they have (as of 2011[update]) so far not been observed and identified with certainty.
Lattice field theory provides a way to study the glueball spectrum theoretically and from first principles. Morningstar and Peardon[1] have computed the masses of the lightest glueballs in QCD without dynamical quarks. The three lowest states are tabulated below. The presence of dynamical quarks would slightly alter these data, but also makes the computations more difficult.
| J PC | mass |
|---|---|
| 0++ | 1730(50)(80) MeV |
| 2++ | 2400(25)(120) MeV |
| 0−+ | 2590(40)(130) MeV |
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