Ψ-resonances, gluons and the Zweig rule

QCD Symmetries in $\eta $- and $\eta '$-Mesic Nuclei

“…One needs extra mass in the flavour-singlet channel associated with non-perturbative topological gluon configurations [16,17], related perhaps to confinement [18] or instantons [19]. SU(3) breaking generates mixing between the octet and singlet states yielding the massive η and η ′ bosons.…”

Comprehensive study of the radiative decays ofJ/ψandψ(2S)to pseudoscalar meson pairs, and search for glueballs

“…In 1972, Fritzsch and Gell-Mann [1] pointed out that "if the quark-gluon field theory indeed yields a correct description of strong interactions, there must exist glue states in the hadron spectrum", and Fritzsch and Minkowski [2] presented a detailed discussion of the phenomenology of the spectrum of what they called "gluestates". The "glue-states", which we here call "glueballs", are bosons with baryon number and isospin equal to zero, and they are SU (3) flavor singlets "to the extent to which SU (3) breaking effect can be neglected" [2].…”

“…The "glue-states", which we here call "glueballs", are bosons with baryon number and isospin equal to zero, and they are SU (3) flavor singlets "to the extent to which SU (3) breaking effect can be neglected" [2].…”

“…Fritzsch and Minkowski [2] have detailed color-singlet states of two and three gluons allowed by conservation rules, which are identical to those for states of two and three photons. The two-gluon states have charge conjugation, C = +1, while the three gluon states can have C = +1 or −1.…”

Two-photon width and gluonic component of

“…The existence of glueballs has been predicted long ago in the early time of QCD as consequence of the self-interaction of gluons and first scenarios have been developed already in 1975 [1]. Today there is agreement on the existence of such states and the lightest state to be a scalar meson.…”