The decays also give some evidence that one of these could be a glueball.

Such a collection forms an unstable particle called a glueball.

The presence of an eta(1405) state also brings glueball mixing into the discussion.

Lattice field theory provides a way to study the glueball spectrum theoretically and from first principles.

A glueball shows up as an extra (supernumerary) particle outside the nonet.

In particle physics, a glueball is a hypothetical composite particle.

Theorists had long known that the glueball, if it existed, would be too short-lived to be observed directly.

The glueball spectrum is the range of masses and spins (and other quantities) that these particles can assume.

No glueball has been demonstrated.

In spite of such seemingly simple counting, the assignment of any given state as a glueball, tetraquark, or hybrid remains tentative even today.

The scalar glueball is also expected to fall in this mass region, appearing in similar fashion to the conventional mesons but having very distinctive decay characteristics.

Consequently, the I.B.M. group believes that fJ(1710) and the glueball are one and the same, and that the existence of glueballs has been virtually proved.

In principle the computational method is fairly simple, but in calculating the kind of results that bear on the glueball problem, enormous numbers of nodes must be taken into consideration.

Since that time calculations within QCD (lattice and sum rules) find the lightest glueball to be a scalar with mass in the range of about 1000-1700 MeV.

M-theory is finished9 Juan has great repute The black hole we have mastered Q.C.D. we can compute10 Too bad the glueball spectrum is still in some dispute11 Ehhhh!

It is possible that the eta and eta prime mesons mix with the pseudoscalar glueball which should occur, in its pure state, somewhere above the scalar glueball in mass.

But the QCD theory also predicts that under certain circumstances, gluons of different types could briefly stick to each other; two gluons thus bound to each other would constitute a hypothetical particle dubbed a "glueball."

As of today, the situation appears somewhat satisfactory for the hadronic spectrum and the computation of the gluon and ghost propagators, but the glueball and hybrids spectra are yet a questioned matter in view of the experimental observation of such exotic states.