ON SOME MODELS OF THE EXOTICHADRON STATESSiniša R. Ignjatović1and Vesna Borka Jovanović21Department of Physics, University...
1. Introduction•first detailed analysis – Jaffe (1977)•first experimental evidence – 2003•pentaquark evidence refuted•some...
Exotic mesons:•Glueballs and hybrids (“ordinary” states)•Multiquarks and meson-meson molecules (“extraordinary” orflavor-e...
2. Tetraquark as a diquark-antidiquark bound state• Lichtenberg model: baryon = diquark + quark (1967)• tetraquark = diqua...
color SU(3)c/light flavor SU(3)f: 3⊗3=3̅⊕6, 3̅⊗3̅=3⊕6̅SU(4)f: 4⊗4=6̅⊕10, 4̅⊗4̅=6⊕1̅0̄̅̃̄̅̆̅antitriplet flavor (spin single...
MethodsAll methods used in the non-perturbative QCD:• Chiral perturbation theory• Lattice QCD• Lattice QCD-inspired models...
3. Other models of four-quark states1. Uncorrelated quarks– Constituent quark model with hyperfine interactions:•spin-colo...
Conclusions1. unlike pentaquarks, tetraquarks are very active topics2. revival of hadron spectroscopy due to the exotic st...
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S. Ignjatović, On Some Models of the Exotic Hadron States

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Balkan Workshop BW2013
Beyond the Standard Models
25 – 29 April, 2013, Vrnjačka Banja, Serbia

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S. Ignjatović, On Some Models of the Exotic Hadron States

  1. 1. ON SOME MODELS OF THE EXOTICHADRON STATESSiniša R. Ignjatović1and Vesna Borka Jovanović21Department of Physics, University of Banja Luka2Institute of Nuclear Sciences Vinča, Belgrade1. Introduction2. Tetraquark as a diquark-antidiquark bound state3. Other models
  2. 2. 1. Introduction•first detailed analysis – Jaffe (1977)•first experimental evidence – 2003•pentaquark evidence refuted•some mesons difficult to interpret as conventional mesons•Conventional hadrons:• mesons: quark+antiquark• baryons: 3 quarks (antiquarks)•Unconventional hadrons allowed by the quark model(and QCD)
  3. 3. Exotic mesons:•Glueballs and hybrids (“ordinary” states)•Multiquarks and meson-meson molecules (“extraordinary” orflavor-exotic states)Models of extraordinary mesons:•tetraquark as bound state of diquark and antidiquark•tetraquark constituted of uncorrelated quarks•meson-meson molecule•states made of mixed conventional and unconventional statesqqqqqq qqqqqqmeson molecule diquark-antidiquark uncorrelated quarksCartoon picture of the four-quark states
  4. 4. 2. Tetraquark as a diquark-antidiquark bound state• Lichtenberg model: baryon = diquark + quark (1967)• tetraquark = diquark + antidiquark (1980’s)• further applications of diquarks: dibaryons (hexaquarks),dense quark matter etc.Diquark – color multiplet – cannot exist outside hadrons3
  5. 5. color SU(3)c/light flavor SU(3)f: 3⊗3=3̅⊕6, 3̅⊗3̅=3⊕6̅SU(4)f: 4⊗4=6̅⊕10, 4̅⊗4̅=6⊕1̅0̄̅̃̄̅̆̅antitriplet flavor (spin singlet, i. e. scalar) states lie~200 MeV below sextet (vector) onesMaking light-flavor tetraquarks:(3̅⊕6)⊗(3⊕6̄̅)=3̅⊗3⊕3̅⊗6̅⊕6⊗3⊕6⊗6̅3̅⊗3=8⊕1 lowest-lying (perhaps the only observable?)
  6. 6. MethodsAll methods used in the non-perturbative QCD:• Chiral perturbation theory• Lattice QCD• Lattice QCD-inspired models• QCD sum rules• Constituent quark model with hyperfine interactions• Heavy quark effective theory
  7. 7. 3. Other models of four-quark states1. Uncorrelated quarks– Constituent quark model with hyperfine interactions:•spin-color or spin-flavor– Different hamiltonians lead to essentially same masses2. Meson-meson molecules– predates quark model itself– within QCD from 1976– resonances near threshold– forces dominated by quark exchange
  8. 8. Conclusions1. unlike pentaquarks, tetraquarks are very active topics2. revival of hadron spectroscopy due to the exotic states3. spectroscopy alone is insufficient to discern between thevarious models4. diquarks are an important concept in non-perturbative QCD

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