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”

qq

q

Q

λq-q

Q

ρq-q

λ mode

ρ mode

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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