Exotics

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) gt 1.5 GeV
2
Exotic Signatures

• Possible signatures for the exotics states
• Exotics quantum numbers
• ? JPC 0-, 1-, 2-, etc
• ? B1 and S1 (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/? radiative decays
• ?? suppressed production (for glueballs)

3
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/? radiative decays
• Results DM2, Mark
• Future BES (?)
• ?? suppressed production
• Results LEP experiments

4
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?KK-?0
68.000 Ev.
pp?KK0?
41.000 Ev.
5
Glueballs

• Lightest states predicted by Lattice QCD JPC
  0,2,0-
• Mass (G.B. West 1997) m(0) lt m(2) lt m(0-)
• -Mixing with the scalar nonet!
• Best candidate for the 0 glueball f0(1500).

E692 pp ? pp(KsKs)
OBELIX (pp)1S0 ? pp-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.
?(1490) JPC 0-
Problem the masses of the candidates are too low
!
7
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
T(1530) ? nK or pK0
uudds
events
ddssu
uussd
?-- ? ?-p- or ?-K-
? ? ?0p 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 !
n2
multipletti qq candidati chirali candidatistati
gluonici candidati ibridi candidati 4 quark
n1