Heavy Quarkonium 2006, June 29, BNL

Double ccbar Production at Belle

SooKyung ChoiGyeongsang University

( For Belle collaboration )

B Golob Belle Lake Louise Winter Inst 2006

e+e- J/ψ + (cc)

• Reconstruct J/ψ → l+l-• the recoil mass against reconstructed J/ψ using

two body kinematics with a known initial energyMrecoil = √(Ecms- E J/ψ )2 - P J/ψ

2 )• X likely contains c c

Belle’s first result• 2002, Belle found large cross-sections for:

(PRL89 142001 (2002))

– e+e- → J/ψ ηc

– e+e- → J/ψ χc0

– e+e- → J/ψ ηc‘

LL~46fb~46fb--11

Belle’s first result continued

• In addition, also observed associated production – e+e- → J/ψ D(*+) X– e+e- → J/ψ D0 X

• Immediately demonstrates large e+e- → J/ψ cc unlike theory prediction

• Based on LUND cc→ D*+/D0

fragmentation rates, calculated:

σσ((ee++ee-- J/J/ψψcc)/cc)/σσ((ee++ee-- J/J/ψψX) X) =0.59=0.59±±0.140.14±±0.120.12

Theoretical predictions

• Color-Singlet e+e- → J/ψ cc was estimated to be very small by Kiselevet al. (1994)– σ~0.05 pb ⇒ should be unobservable

even at high luminosity B-factories

• Color-octet e+e- → (cc)8 g → J/ψ g (with ⟨Oncc⟩ fixed to Tevatron and others data) should not be large as well (but can be significant around the end-point of J/ψ momentum) Braaten-Chen (1996)

• Color-Singlet e+e- → J/ψ ggdominates! Predicted σCS~1-2 pbCho-Leibovich (1996)

Using more data

• Belle 2004: Full analysis of double charmoniumproduction (PRD70 071102 (2004))

• Reconstructed charmonium:– J/ψ– ψ(2S)

LL~140fb~140fb--11

Cross-sections

• Interesting: – Orbital excitations are not suppressed!– Only S,P states are seen recoiling to J/ψ (spin=1)!

ηc J/ψ χc0 χc1+χc2

ηc(2S)

<5.3<8.6

16.5±1.7±0.4 16.3±4.6±3.9

ψ(2S)

6.4±1.7±1.0 12.5±3.8±3.1

<9.1 <16.9

<9.1 <16.9

J/ψψ(2S)

25.6±2.8±3.4 16.3±4.6±3.9

• Born cross-sections: σ * BR (recoil charmonium → >2charged)

R e c o i l

Recon

struc

ted

Can theory accommodate this result

• The first NRQCD estimates: R=σJ/ψηc/σμμ~αs

2(mcv/Ebeam)6

– σ(e+e-→J/ψηc)=2.3±1.1 fb. (~10 times too low)

• Are there backgrounds from double photon annihilation e+e-→ J/ψ J/ψ?– Bodwin-Braaten-Lee 2003; confirmed

by Liu-He-Chao, Brodsky-Ji-Lee

• Glueball ? – Brodsky-Goldhabor-Lee

gg

Calibrate recoil mass scale with e+e- γ ψ’; ψ’ π+π−J/ψ

This translates to δMx ‹ 3 MeVfor Mx~3GeV.

(inbiased MC)

(data w.r.t. MC)

Include e+e- J/ψ J/ψ, etc in fitJ/ψ χ c1,2

σσ((e+ee+e-- J/J/ψψcc)cc)σσ((e+ee+e-- J/J/ψψX)X)=0.82=0.82±±0.150.15±±0.140.14

Preliminary !! Preliminary !! (since 2003)(since 2003)

BaBar confirmation• 2005, BaBar also see

double charmoniumevents – e+e- → J/ψ ηc

– e+e- → J/ψ χc0

– e+e- → J/ψ ηc‘

Angular analysis

~ (1+αp,h cos2θp,h)

Xθhel

θprod

dN

dθp,h

l+

•• Fit Fit MMrecoilrecoil(J(J//ψψ) in bins of J/) in bins of J/ψψ production and production and helicityhelicity anglesangles

•• Correct efficiencyCorrect efficiency•• Fit with ~(1+Fit with ~(1+ααcoscos22θθ))

αprod αhel αprod=αhel Lmin NRQCD+1.0-1.0+1.0

+1.0+0.25+1.0

+0.93+0.87-0.47

-1.01+0.38-0.33

+0.87+0.86-0.63

glueballηc

χc0ηc’

+1.4+1.1-0.8

-1.7±0.5+1.9+2.0

-1.2

+0.5+07-0.5

-0.5+0.7-0.5

+0.3+1.0-0.7

-1.0-1.0-1.0

No significant J/ψ J/ψcontaminationto J/ψ ηc signal peak

• Mass scale correct– within +- 3MeV

• Angular distribution consistent with VP

New ideas ?• Need to solve an order of magnitude disagreement– Kaydalov 2003. NRQCD is wrong! Use instead Regge

trajectories approach – tune free parameters from D meson production ⇒ get reasonable agreement for e+e-

→ J/ψcc (σ~1 pb) and predict ~10% of J/ψcc are double charmonium (Mcc <2MD)

– Bondar Chernyak 2005. Try to save NRQCD! Light cone expansion formalism. Use wider wave functions. Manage to “predict” σ (e+e- → J/ψ ηc )~30 fb

– Braguta Likhoded Luchinsky 2006. Similar approach to BC applied for all final states: reasonable agreement

• All approaches are phenomenological. Need to predict something that can be checked.

New state(hep-ex/0507019)

• Add more data and extend searching region above DD threshold• New peak at M~3.9 GeV, Temporary called X(3940)• Two peaks are not excluded, but the second is not significant with the present statistics• Significance 5.0 σ• Γ=39 ± 26 MeV(< 93MeV @ 90%C.L.)• σ×Br(X(3940) → >2 charged tracks) =10.6±2.5±2.4 fb

LL~357fb~357fb--11

X(3940) decays• X→DD or DD* ? – Reconstruct J/ψ & one D – See the Mrecoil(D J/ψ)– observe an unreconstructed D & D*–– D and D* are well D and D* are well separated ~2.5separated ~2.5σσ

X(3940) → DD(*)

• X (3940)→DD*:Clear peak

• N=24.5 ±6.9 (5.0σ)Γ=15.1±10.1 MeVM=3.943±0.006 GeV

B (X(3940)→DD*)= (96+45

-32±22)%

• X(3940)→DD: no signal• N = 0.2+ 4.4

-3.5 < 8.1B (X(3940)→DD)<41%@ 90 C.L.

X(3940) ωJ/ψ

• Reconstruct ω & one J/ψ• N = 1.9+3.2

-2.4 < 7.6 @90% C.L• B (X(3940)→DD)<41% @ 90 C.L.• X(3940) doesn’t decay into J/ψ ω

Summary

• e+e- J/ψ cc much higher than NRQCD predictions

• e+e- J/ψ ηc: NRQCD predicts 2.3pb, Expt>25.6 pb

• “Post”dictions from Bondar-Chernyak & Braguta Likhoded Luchinsky Seem to work

• Are these resonable? Does NRQCD need modification

• New state seen @ M=3943 MeV– decays to DD*; not seen in DD or ωJ/ψ