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## Exotic meson
Non-quark model mesons include **exotic mesons**, which have quantum numbers not possible for mesons in the quark model;**glueballs**or**gluonium**, which have no valence quarks at all;**tetraquarks**, which have two valence quark-antiquark pairs; and**hybrid mesons**, which contain a valence quark-antiquark pair and one or more gluons.
All of these can be classed as mesons, because they are hadrons and carry zero baryon number. Of these, glueballs must be flavor singlets; that is, have zero isospin, strangeness, charm, bottomness and topness. Like all particle states, they are specified by the quantum numbers which label representations of the Poincaré symmetry, ie, J is the angular momentum, P is the intrinsic parity and C is the charge conjugation parity) and by the mass. One also specifies the isospin I of the meson.
Typically, every quark model meson comes in SU(3) flavor nonet: an octet and a flavor singlet. A glueball shows up as an extra ( ## Additional recommended knowledge
## Lattice predictionsLattice QCD predictions for glueballs are now fairly stable, at least when virtual quarks are neglected. The two lowest states are **0**with mass of^{+ +}**1611±163**MeV and**2**with mass of^{+ +}**2232±310**MeV.
The 0 are all expected to lie above 2 GeV. Glueballs are necessarily isoscalar, with isospin ^{− −}I=0.
The ground state 1, ^{− +}1 and ^{− −}2 all lie a little below 2 GeV. The hybrid with exotic quantum numbers ^{− +}1 is at ^{− +}1.9±0.2 GeV. The best lattice computations to date are made in the quenched approximation, which neglects virtual quarks loops. As a result, these computations miss mixing with meson states.
## The
^{+ +} |

Particles in physics | |
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Elementary particles | Fermions:Quarks: u · d · s · c · b · t • Leptons: e^{-} · e^{+} · μ^{-} · μ^{+} · τ^{-} · τ^{+} · ν_{e} · ν_{μ} · ν_{τ} Bosons:Gauge bosons: γ · g · W^{±} · Z^{0}_{ } GhostsOther:^{ } |

Composite particles | Hadrons:Baryons(list)/Hyperons/Nucleons: p · n · Δ · Λ · Σ · Ξ · Ω · Ξ_{b} • Mesons(list)/Quarkonia: π · K · ρ · J/ψ · Υ Other:Atomic nuclei • Atoms • Exotic atoms: Positronium • Molecules |

Hypothetical elementary particles | Axino · Dilatino · Chargino · Gluino · Gravitino · Higgsino · Neutralino · Sfermion · Slepton · Squark Superpartners: Axion · Dilaton · Goldstone boson · Graviton · Higgs boson · Tachyon · X · Y · W' · Z'Other: |

Exotic hadrons:Exotic baryons: Pentaquark • : Glueball · Tetraquark Exotic mesons Mesonic moleculeOther: | |

Quasiparticles | Davydov soliton · Exciton · Magnon · Phonon · Plasmon · Polariton · Polaron |