Possible Interpretations of DsJ(2632)

Shi-Lin Zhu

Peking UniversityQWG2004

October 14, 2004

Collaborators: Y.-B. Dai, C. Liu, Y.-R. LiuHep-ph/0407157 (PRD in press)

Hep-ph/0408234

Advances in Hadron Spectroscopy Since 2003

• BES: pp_bar near-threshold enhancement in J/Psigamma pp_bar decays, I=0 channel; p Lambda_bar threshold enhancement in J/Psi K p Lambda_bar

• BABAR/CLEO/BELLE: narrow states DsJ(2317), DsJ(2457) below threshold

• LEPS and others found evidence of Pentaquarks!• BELLE/CDFII: new narrow state X(3872)• E852: two exotic mesons with JPC=1-+ at 1709/2001MeV• SELEX: narrow state DsJ(2632) above threshold with abno

rmal decay pattern

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SELEX observed DsJ(2632) inDs

+ eta and D0K+ modes

7.2 sigma 5.3 sigma

49.3 events 14 events

2+ state in (1+, 2+)

doublet in HQET

2

BABAR, CLEO, FOCUS didn’t see DsJ(2632)

3

SELEX:

• fixed-target hadroproduction

• 600 GeV Sigma- beam which consists strange quark explicitly

• looks at very large Xf, not available for e+e- colliders

• Production: gluon-gluon fusion

BABAR/CLEO:

• e+e- colliders , center of mass close to Upsilon

• Production: e+e- annihilation

FOCUS:

• photoproduction

• doesn't see double-charm hadrons but they exist!

Non-observation of a particular state in certain experiments does not exclude its possible existence

The production ratios of different charm states could be quite different between e+e- annihilation and gluon-gluon fusion

According to Evdokimov at SELEX: If DsJ(2632) really exists Special mechanism in hadroproduction at large Xf

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Three Puzzles of DsJ(2632) If Not Artifact

• Narrow decay width. 274 MeV above D0K+ and 116 MeV above Ds eta threshold, decay width less than 17 MeV. Naive expectation around (100~200) MeV

• Is DsJ(2632) a cs_bar state? L=0: [Ds(1968), D*

s (2112)] L=1, lP=1/2+: [DsJ (2317), DsJ (2457)] L=1, lP=3/2+: [DsJ (2536), DsJ (2573)] Too low for L=2 assignment Is it the first radial excitation of D*

s (2112)? (K.-T. Chao)• Unusual decay pattern SU(3)F symmetry + cs_bar assignment SELEX

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DsJ(2632) As a Tetraquark

Version I: (Liu, Zhu, Dai, Liu)

• • 0+ isoscalar member in 15 rep., the ratio of SU(3) C-G coefficients

naturally explains its anomalous decay pattern:

• Quark content:

• Mass:

• Decay pattern:

SU(3) C-G Decay Momentum

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Weight Diagram of Heavy Tetraquark Multiplets

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Version II: (Chen, Li; Gupta)

• Quark content: fluctuates into

Hence main decay mode is

• D0K+ requires , component, OZI suppressed

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Version III: (Chao)

• Tightly bound diquark configuration which has small mixing with ,

narrow total width• Mixing between unusual decay p

attern

Version IV: (Maiani;Nicolescu)

• Quark content: • D0K+ suppressed while important• Decay pattern: • Prediction:

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Problems With Tetraquark Scheme

• There should be many other tetraquark partners of DsJ(2632). Where are they?

• Its narrow width may require that quarks inside Ds

J(2632) form tightly bound clusters like diquarks. Otherwise tetraquarks fall apart easily.

• The first three versions of tetraquarks predict the same production rates for D+K0, D0K+ final states. The fourth version predicts very large D+K0 mode.

• But SELEX didn't find any signal in the D+K0 channel!

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DsJ(2632) as Radial Excitation• First radial excitation of Ds(2112) with JP=1- (Chao; B

arnes et al.;Bereven, Rupp)

• The nodal structure of its radial wave function ensures the narrow total width

• Different decay momentum in two channels leads to anomalous decay pattern

• Dynamical calculation very desirable and missingFuture experimental search for: (Dai, Liu, Liu, Zhu)

• its SU(3) flavor partners DJ0,+(2530)

• its B-meson analogues BJ 0,+(5840), BsJ+(5940)

• S-wave two pion decay modes

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Large Nc And DsJ(2632) As A Hybrid

Meson: Version I (Dai, Liu, Liu, Zhu)

• In the large Nc limit, the dominant decay mode is for the gluon to split into a color-octet

• recombines with pair to form

• The Nc order of this decay amplitude is

• No abnormal decay pattern as observed in SELEX

• This assignment not preferred!

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Version II: Hybrid Scheme (Dai, Liu, Liu, Zhu)

• Decay mode (b) into glueball is dominant, Nc

0, forbidden by kinematics

• The subleading mode (c) into becomes dominant; is mixture of and

Ds eta dominant

• D0K+ can occur via mode (a)

• c s_bar is color-singlet, additional 1/Nc suppression from color mismatch, its Nc order

•

But its mass and decay width needs dynamical calculation!

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Summary• SELEX observed DsJ(2632) but BABAR,

CLEO, FOCUS didn’t see it.

• It could be an artifact.

• If it really exists, it could be

- Tetraquark

- Radial excitation

- Heavy hybrid meson

- …

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