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Diquarks in heavy baryons

Atsushi Hosaka (RCNP, Osaka U. ）. Practical questions of hadron physics. • How ground and excited states are described? • Are there simple language for it when quarks and gluons interact strongly • Are there kinds of quasi-particles interacting weakly • Constituent quarks:

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Diquarks in heavy baryons

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  1. Atsushi Hosaka(RCNP, Osaka U.） Practical questions of hadron physics • How ground and excited states are described? • Are there simple language for it when quarks and gluons interact strongly • Are there kinds of quasi-particles interacting weakly • Constituent quarks: Mere useful tool of symmetry realization or Dynamically realistic and active object • How can diquarksbe be identified in multi-quark systems Baryons, nuclei, nuclear matter, quark matter Diquarks in heavy baryons Charmed baryons

  2. Quark-diquark baryon Selem-Wilczek: e-Print: hep-ph/0602128 • ee has repulsive force, BUT • qq has attractive force SU(3)c: half of qqbar attraction SU(2)c : Same as qqbar Pauli-Gursey symmetry ~ several hundred MeV • Diquark can be seen better in heavy baryons than in light GoodBad Color magnetic int.

  3. Some evidences • Σ-Λ (80 MeV), Σc-Λc (215 MeV) mass difference • Production rate of Λ, Σ (e+e-@10 GeV) Λ : Σ = 0.08:0.023, Λc: Σc= 0.074:0.014 • ΔI = ½ rule • F2n/F2p ¼ • Lack of exotics Repulsive between good diquarks? Charmed baryons

  4. In QCD • How diquarks are defined? -- correlation function ud-diquark Heavy quark qq interaction in a baryon (colored environment) • How are they observed in charmed baryons? Spectrum, decay rate, production t = 0 t 2t • Are there other opportunities to hunt diquarks? Charmed baryons

  5. Density correlations r = 0.69 fm Alexandrou, deForcrand, Lucini PRL 97, 222002 (2006) r = 0.47 fm Good diquark Bad diquark r θ r = 0.35 fm Indicates significant attraction between quarks in good diquark pair 1.0 cosθ Charmed baryons

  6. Baryon spectrum Light flavor baryons (uds) c S=1/2 S=3/2 qcc qqc uds qqq I Ground 8 + 10 and excited ~ 80 states Charmed baryons

  7. Charmed baryons 14c ＋1cc << 80uds S=3/2 (6excited) ? [GeV] ? 5/2+ 1/2– ? 3/2+ 3/2+ 3/2 – 1/2+ ΩC Ξ’C 1/2 – 3/2+ css ΞC S=1/2 1/2+ ΞC 1hω csq 1/2+ 1/2+ 1Ξ+cc cqq cqq Charmed baryons

  8. Advantage of heavy quark • Discriminate of modes Light baryon Two HQ baryon One HQ baryon • Spectrum, productions and decays Charmed baryons

  9. “Q” may isolate “qq” • λ and ρ motions split  known as isotope shift sqsq, SO Λc(1/2-,1/2- 3/2-,3/2-, 5/2-) ρ q-q q-q q Σc(1/2-,3/2-) q λ ρ mode Σc(1/2-,1/2- 3/2-,3/2-,5/2-) q Q Q Λc(1/2-,3/2-) λ mode Σc(1/2+,3/2+) G.S. Λc(1/2+) Charmed baryons

  10. Decays λ-mode ρ-mode Ratio: ρ-modeバリオンは軽い中間子と重いバリオンに λ-mode　　　　　　　重い　　　　　　軽い　　　　　に崩壊 Charmed baryons

  11. 1/2– 1/2+ E1 transition λ mode ρ mode Good diquark 0+ 3P0 diquark 0– lρ = 1 lλ = 1 0– 0+ is forbidden Good diquark 0+ Charmed baryons

  12. 5/2– 1/2+ M2, E3 transition λ mode ρ mode 3S1diquark 1+ 3P2diquark 2– lρ = 1 lλ = 1 2– 0+ is M2 Both M2 E3 Good diquark 0+ Charmed baryons

  13. Role of a heavy quark • Filter out 2-body correlations • Excitation spectru, λ-ρ modes, Good vs bad diquark • Decay pattern, selection rules • Diquarkdensities Establish diquarks from QCD  Phenomena Charmed baryons

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