Exotics & Glueballs QCD suggests the existence of non states like:
Glueballs (gg,ggg): mesons made of bound gluons.
Hybrids ( ): qqbar pairs with an excited gluon.
Multiquark states ( , , ) and/or meson molecules. Many new states foreseen New multiplets !
Possible mixing with the standard mesons
(especially for glueballs).
Mass range (from lattice QCD predictions): > 1.5 GeV
Exotics & Glueballs QCD suggests the existence of non states like:
Glueballs (gg,ggg): mesons made of bound gluons.
Hybrids ( ): qqbar pairs with an excited gluon.
Multiquark states ( , , ) and/or meson molecules. Many new states foreseen New multiplets !
Possible mixing with the standard mesons
(especially for glueballs).
Mass range (from lattice QCD predictions): > 1.5 GeV
Exotic Signatures Possible signatures for the exotics states:
Exotics quantum numbers
JPC = 0+-, 1-+, 2+-, etc
B=1 and S=1 (no standard baryons or mesons)
No place in the standard meson nonets
Decay width not compatible with QCD predictions for standard states
Enhanced production in gluon rich environments (for glueballs):
Central production
ppbar annihilation
J/ψ radiative decays
suppressed production (for glueballs)
Experimental strategy For example for Glueball search one exploits the preferred production reactions like:
Central production (DPE) Results: WA102, Gams
Future: GTeV (?) , HERAg (No)
ppbar annihilation
Results: Obelix, Crystal Barrel,BNL
Future: PANDA
J/ψ radiative decays
Results: DM2, Mark
Future: BES (?)
suppressed production
Results: LEP experiments 1 2
For the quantum numbers dan the decay width determination coupled channel and spin-parity analyses are mandatory ! pp+-0 ppK+K-0 ppK±K0± LH NP LP 1.500.000 Ev. 68.000 Ev. 41.000 Ev. Obelix
Glueballs Lightest states predicted by Lattice QCD: JPC = 0++,2++,0-+
Mass (G.B. West 1997) : m(0++) < m(2++) < m(0-+)
-Mixing with the scalar nonet!
Best candidate for the 0++ glueball: f0(1500). * Morningstar &
Peardon 1999 E692
pp pp(KsKs) WA102
pp pp(K+K-) M2(+-) OBELIX
(pp)1S0 p+p-p0
Hybrids Light states predicted with Mass ~ 2GeV.
Best candidates: OBELIX
pp K± K0p± p+ p- Exotic number:
JPC = 1-+
M = 1370 GeV
Seen also by Crystal Barrel in the pn p-p0h
reaction. η(1490): JPC = 0-+ Problem: the masses of the candidates are too low ! E852
p-p hp-p
Multiquark states Θ+(1530) → nK+ or pK0 Ξ-- → Ξ-π- or -K- Ξ+ → Ξ0π+ or +K0 ddssu uussd uudds The anti-decuplet proposed by Diakonov, Petrov & Polyakov (Z.Phys.A359 (1997) 305) with the three exotic baryons at the corners - requiring the indicated five valence quarks - and their decay modes.
Masses: 1530 MeV and 2070 MeV invariant mass [GeV/c2] events CLAS SPring-8 Many evidence, but small significance. Not yet clear !
multipletti qq
candidati chirali
candidatistati gluonici
candidati ibridi
candidati 4 quark n=1 n=2 Molti candidati e molto lavoro da fare per chiarire la situazione !
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