Diquarks in heavy baryonsAtsushi Hosaka (RCNP, Osaka U. )
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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 diquarks be be identified in multi-quark systems Baryons, nuclei, nuclear matter, quark matter
Quark-diquark baryonSelem-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
Color magnetic int.Good Bad
Some evidences
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• 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/F2
p ¼
• Lack of exotics Repulsive between good diquarks?
In QCD
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• How diquarks are defined? -- correlation function
ud-diquark Heavy quark
t = 0 2t t
• How are they observed in charmed baryons?Spectrum, decay rate, production
• Are there other opportunities to hunt diquarks?
qq interaction in a baryon (colored environment)
Density correlations
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Alexandrou, deForcrand, LuciniPRL 97, 222002 (2006)
cosθ 1.0
r
θ
r = 0.69 fm
r = 0.47 fm
r = 0.35 fm
Good diquarkBad diquark
Indicates significant attraction between quarks in good diquark pair
Baryon spectrum
S=1/2 S=3/2
qqq
qqcqcc
c
I
Light flavor baryons (uds)
Ground 8 + 10 and excited ~ 80 states
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uds
S=3/2
S=1/2
Charmed baryons 14c + 1cc << 80uds (6excited)
1/2+
1/2 –
1/2+
3/2+
1/2–
1/2+
3/2+
3/2 –
5/2+
?
ΞC
[GeV]
?
1/2+
3/2+
ΩC
cqq cqq
csq
cssΞC
Ξ’C
1hω
?
1 Ξ+cc
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Advantage of heavy quark• Discriminate of modes
Light baryon One HQ baryon Two HQ baryon
• Spectrum, productions and decays
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• λ and ρ motions split known as isotope shiftsqsq, SO
Σc(1/2-,3/2-)
Λc(1/2-,1/2-
3/2-,3/2-, 5/2-)
Λc(1/2-,3/2-)
Σc(1/2-,1/2-
3/2-,3/2-, 5/2-)
Σc(1/2+,3/2+)
Λc(1/2+)
“Q” may isolate “qq”
q
Q
λq-q
Q
ρq-q
λ mode
ρ mode
G.S.9/10-13, 2013 Charmed baryons 9
Decays
Ratio:
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ρ-mode λ-mode
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
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1/2– 1/2+ E1 transition
λ modeGood diquark 0+
lλ = 1
3P0 diquark 0–
lρ = 1
ρ mode
0– 0+ is forbidden
Good diquark 0+
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5/2– 1/2+ M2, E3 transition
λ mode3S1 diquark 1+
lλ = 1
3P2 diquark 2–
lρ = 1
ρ mode
2– 0+ is M2
Good diquark 0+
Both M2 E3
Role of a heavy quark
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• Filter out 2-body correlations • Excitation spectru, λ-ρ modes, Good vs bad diquark• Decay pattern, selection rules• Diquark densities
Establish diquarks from QCD Phenomena