GlueX Physics Exotic Quantum Number Mesons

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GlueX Physics

Review Papers

Mesons in the Quark Model

Exotic Quantum Number Mesons

Exotic Quantum Numbers

As noted in the Quark Model chapter, simple q{\bar  q} systems can have the following JPC quantum

0-+, 0++, 1--, 1+-, 1++, 2--, 2-+, 2++, 3--, 3+-, 3++, .... (1)

It was also noted that there were a number of JPC quantum numbers that are not

allowed for q{\bar  q} systems:

0--, 0+-, 1-+, 2+-, 3-+, .... (2)

Observation of a state from equation (2) would indicated something outside the simple quark model picture. Such states could include multi-quark states such as q{\bar  q}q{\bar  q}, glueballs (states containing only gluons) gg,ggg, or hybrid mesons, written schematically as q{\bar  q}g. In fact, the manifest glue represents an excitation of the gluonic field binding the q{\bar  q} system. For a more detailed description of the statos these states, please consult the recent review papers mentioned in this note. Various models make predictions for expected quantum numbers and masses for these states.

Naming Conventions

The notation used throughout this article to represent hybrid mesons is that which is currently in use by the Particle Data Group. In their notation, the parity and charge conjugation determine the name of the hybrid, which is taken as the name of the normal meson of the same J,P,C and isospin. The total spin is then used as a subscript to the name. The PDG naming scheme for mesons with non q{\bar  q} quantum numbers is given in Table 1.

JPC (IG) (IG) (I)
0-- (1+) ρ0 (0-) ω0'0 (1/2) K*0
0+- (1+) b0 (0+) h0,h'0 (1/2) K*0
1-+ (1-) π1 (0+) η1'1 (1/2) K*1
2+- (1+) b2 (0+) h2,h'2 (1/2) K*2
3-+ (1-) π3 (0+) η3'3 (1/2) K*3

Table 1: The naming scheme for exotic quantum-number mesons.

There is also an alternate naming scheme that may be seen in older papers. It relied on the spin and parity to define the name, and put a hat over the name with the wrong C-parity. It is shown in Table 2.

JPC (IG) (IG) (I)
0-- (1+) {\hat  \pi }0 (0-) {\hat  \eta }0,{\hat  \eta }'0 (1/2) K*0
0+- (1+) {\hat  a}0 (0+) {\hat  f}0,{\hat  f}'0 (1/2) K*0
1-+ (1-) {\hat  \rho }1 (0+) {\hat  \omega }1,{\hat  \phi }1 (1/2) K*1
2+- (1+) {\hat  a}2 (0+) {\hat  f}2,{\hat  f}'2 (1/2) K*2
3-+ (1-) {\hat  \rho }3 (0+) {\hat  \omega }3,{\hat  \phi }'3 (1/2) K*3

Table 2: An older naming scheme for exotic quantum-number mesons. This is no longer in common use.

Models of non q{\bar  q} Mesons

The Bag Model

QCD Sum Rules

The Flux-tube Model

JPC (IG) (IG) (I)
1++ (1-) a1 (0+) f1,f'1 (1/2) K1
1++ (1+) ρ1 (0-) ω11 (1/2) K*1
0-+ (1-) π0 (0+) η0'0 (1/2) K0
1-+ (1-) π1 (0+) η1'1 (1/2) K*1
2-+ (1-) π2 (0+) η2'2 (1/2) K2
0+- (1+) b0 (0+) h0,h'0 (1/2) K*0
1+- (1+) b1 (0+) h1,h'1 (1/2) K1
2+- (1+) b2 (0+) h2,h'2 (1/2) K*2

Table 2: The naming scheme for hybrid mesons from the flux-tube model.

Lattice Calculations

Here we present a brief summary of lattice results related to exotic quantum number mesons. A more detailed description can be found in the section on Lattice QCD Calculations.

The Experimental Situation

The π1(1400)

The π1(1600)

The π1(2015)


  • Experimental Measurements
    • Precision Meson Spectroscopy at COMPASS, The COMPASS Collaboration, arXiv:1002.1272, (2010), arXiv.
    • Observation of a JPC=1-+ exotic resonance in diffractive dissociation of 190 GeV/c pi- into pi- pi- pi+, The COMPASS Collabration, arXiv:0910.5842, (2009), arXiv.
    • Search for the photo-excitation of exotic mesons in the π+ π+ π- system, M. Nozar, et al. (CLAS Collaboration), Phys. Rev. Lett. 102 (2009), 102002, PRL.
    • Partial wave analysis of the π-π-π+ and π-π0π0 systems and the search for a JPC=1-+ meson, A.R. Dzierba, et al., Phys. Rev. D73, (2006), 072001, PRD.
    • Exotic Meson Decays to ω πoπ-, M. Lu et al. (E852 Collaboration), Phys. Rev.94, (2005), 032002, PRL.
    • Study of the Reaction π-p → η' π0 n at the VES Spectrometer, Y. Guoz (VES Collaboration), AIP Conf. Proc. 717 (2004) 145-149.
    • Exotic Meson Production in the f1(1285) π<sup-</sup> System observed in the Reaction π-p → η π+ π- π- p at 18 GeV/c, J. Kuhn (E852 Collaboration), Phys. Lett. B595, (2004), 109-117, Science Direct.
    • ρ π states in the anti-proton neutron annihilation into π- 3π0, F. Meyer-Wildhagen et al. (Crystal Barrel Collaboration), Nucl. Phys. A721 (2003), 605-608, Science Direct.
    • Exotic and qq̅ resonances in the ππ-π- system produced in π- p collisions at 18 GeV/c, S.U. Chung, et al. (E852 Collaboration), Phys. Rev. D65, (2002),1-16,PRD.
    • Observation of Exotic Meson Production in the Reaction π-p→ η' π- p at 18 GeV/c , E.I. Ivanov (E852 Collaboration), Phys. Rev. Lett.86 (2001), 3977.
    • Study of reaction π-A → π+ π- π- A at VES setup, I. Kachaev (VES Collaboration), (2001), arXiv.
    • The JPC=1−+ hunting season at VES, V. Dorofeev (VES Collaboration), (2001), arXiv.
    • Evidence for a ηπ-wave with odd angular momentum in antiproton-proton-annhilations at rest into π0π0η, A. Abele et al. (Crystal Barrel Collaboration), Phys. Lett. B446 (1999), 349, Science Direct.
    • Observation of a New JPC)=1-+ Exotic State in the Reaction π-p→π+π-π-p at 18 GeV/c, G.S. Adams (E852 Collaboration), Phys. Rev. Lett. 26 (1998), 5760.
    • Exotic ηπ State in antiproton-deuterium Annihilation at Rest into ηπ-π0 pspectator, A. Abele et al. (Crystal Barrel Collaboration), Phys. Lett. B423 (1998), 175.
    • Study of resonance production in diffractive reaction π- A → π+ π- π- A, D.V. Amelin (VES Collaboration), Phys. Lett. B356, (1995), 595, Science Direct.
    • Study of π- N → η π- N and π- N → η' π- N reactions at 37-GeV/c, G.M. Beladidze (VES Collaboration), Phys. Lett. B313, (1993), 276-282.
  • Model Calculations and Interpretations
    • Study of the eta pi and eta-prime pi spectra and interpretation of possible exotic JPC=1-+ mesons, A.P. Szczepaniak, M. Swat, A.R. Dzierba and S. Teige, Phys. Rev. Lett. 91 (2003), 092002, PRL.

Lattice QCD Calculations


Strong Decay Models