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Exotics & Glueballs

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.

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Exotics & Glueballs

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  1. 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

  2. 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)

  3. 1 2 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

  4. Obelix For the quantum numbers dan the decay width determination coupled channel and spin-parity analyses are mandatory ! LH NP LP pp+-0 1.500.000 Ev. ppK+K-0 68.000 Ev. ppK±K0± 41.000 Ev.

  5. * Morningstar & Peardon 1999 WA102 pp  pp(K+K-) 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). E692 pp  pp(KsKs) OBELIX (pp)1S0 p+p-p0 M2(+-)

  6. Hybrids Light states predicted with Mass ~ 2GeV. Best candidates: E852 p-p  hp-p 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 !

  7. SPring-8 CLAS Multiquark states 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 Θ+(1530) → nK+ orpK0 uudds events ddssu uussd Ξ--→Ξ-π- or-K- Ξ+→Ξ0π+ or+K0 invariant mass [GeV/c2] Many evidence, but small significance. Not yet clear !

  8. Molti candidati e molto lavoro da fare per chiarire la situazione ! n=2 multipletti qq candidati chirali candidatistati gluonici candidati ibridi candidati 4 quark n=1

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