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  J PC = 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1 22

For the quantum numbers dan the decay width determination coupled channel and spin-parity analyses are mandatory ! pp   +  -  0 pp  K + K -  0 pp  K ± K 0  ± LHNPLP Ev Ev Ev. Obelix

Glueballs Lightest states predicted by Lattice QCD: J PC = 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: f 0 (1500). * Morningstar & Peardon 1999 E692 pp   pp(KsKs) WA102 pp   pp(K + K - ) M2(+-)M2(+-) OBELIX (pp) 1 S 0       

Hybrids Light states predicted with Mass ~ 2GeV. Best candidates: OBELIX pp   ±     ±      Exotic number: J PC = 1 -+ M = 1370 GeV Seen also by Crystal Barrel in the pn       reaction. η(1490): J PC = 0 -+ Problem: the masses of the candidates are too low ! E852   p     p

Multiquark states Θ + (1530) → nK + or pK 0 Ξ -- → Ξ - π - or  - K - Ξ + → Ξ 0 π + or  + K 0 ddssuuussd 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 !