1. Decoding the riddle of Y(4260) and Zc(3900) Qiang Zhao
Institute of High Energy Physics, CAS
Decoding the riddle of Y(4260) and Zc(3900)
Qiang Zhao
Institute of High Energy Physics, CAS
and Theoretical Physics Center for Science Facilities (TPCSF), CAS
Q. Wang, C. Hanhart, QZ, [hep-ph]
The 9th International Workshop on Heavy Quarkonium, April 22-26, Beijing

2. Outline 1. Status of XYZ states – A jigsaw puzzle?
2. The nature of Y(4260) and Zc(3900)
3. Can we fit in some of the pieces of the jigsaw puzzle?

3. 1. Status of XYZ states – A jigsaw puzzle?

4. S=0,1 c c L J=L+S Charged charmonium spectrum
-- A completely new scenario of strong QCD!
States close to open thresholds
-- The role played by open D meson channels?
Close to DD* threshold
S=0,1 c c L
J=L+S

5. Close to DD* threshold
[hep-ph]
X(3872)
X(3900)
Close to DD* threshold
Y(4260)
Y(4360)

6. Observation of Y(4260)
PRD77, (2008)
Belle

7. [(5S) (1,2,3S) +–] >> [(4,3,2S) (1S) +–]
(11020)
11.00
(10860)
partial width (keV) – +
10.75
260 Zb
(4S)
2M(B)
10.50 2 +
(3S)
Mass, GeV/c2
hb(2P)
10.25
430 1
b(2S)
(2S)
10.00
hb(1P)
290 6
9.75
9.50
(1S)
b(1S)
Belle, Phys. Rev. Lett. 108 (2012)

8. Belle, arXiv:1105.4583[hep-ex]; PRL108, 22001 (2012)
Heavy quark symmetry breaking?

9. (5S)→B*B(*)π: Results
Branching fractions of (10680) decays (including neutral modes):
BBp < 0.60% (90%CL)
BB*p = 4.25 ± 0.44 ± 0.69%
B*B*p = 2.12 ± 0.29 ± 0.36%
Assuming Zb decays are saturated by the already observed (nS)π, hb(mP)π and B(*)B* channels, one can calculate complete table of relative branching fractions:
NEW!
Belle PRELIMINARY
B(*)B* channels dominate Zb decays !
A. Bondar at ICHEP2012

10. Resonant structure of (2S)00
Dalitz plot analysis
with Zbs
without
NEW!
Clear Zbs signals are seen in (2S)π0π0
Significance of Zb(10610) is 5.3σ (4.9σ with systematics)
Zb(10650) is less significant (~2σ)
Fit to the Zb(10610) mass gives M=10609±8±6 MeV
M(Zb )= ±2.0 MeV +
Belle PRELIMINARY
A. Bondar
at ICHEP2012 10 10

11. It could be an opportunity for understanding the mysterious Y(4260).
The mass of the charged charmonium-like structure Zc(3900) is about GeV.
It could be an opportunity for understanding the mysterious Y(4260).
BESIII, arXiv: [hep-ex], talk by Z.Q. Liu

12. Belle, arXiv:1304.0121v1 [hep-ex], talk by C.P. Shen
Xiao et al., arXiv: v1 [hep-ex], see talk by K. Seth

13. Brief summary of the exp. progress
New quarkonium-like states, i.e. X, Y, Z’s, are observed in experiment
Do not fit in the conventional quarkonium spectrum as quark-antiquark states, e.g. X(3872), Y(4260), X(3900) etc.
Most of these new states, such as X(3872), are located close to a two-particle threshold.
Evidence for charged quarkonium states, e.g. Zb(10610), Zb(10650) and Zc(3900).
In some cases, isospin or heavy quark symm. are violated.
Good candidates for hadronic molecules or other non-standard configurations, e.g. tetraquarks, hybrids, etc.

14. 3. The nature of Y(4260) and Zc(3900)

15. i) Charmonium production in ee    final particles
Direct production of vector charmonium states
Dynamics for charmonium interactions with final states
Signals for exotics? Y(4260), X(3900) ?
Any opportunities for understanding the vector charmonium spectrum? …… e+ *
1, / …
… … e
Belle, BaBar, and BESIII

16. Cross section lineshape in e+e- annihilations
(3770), 1D
X(3900) ?
(4040), 3S
e+e-  DD
(4160)
(4415)
What is X(3900)? (see Wang et al., PRD84, (2011))
X(3900) has not been inlcuded in PDG2010 and PDG2012.
Not in charmonium spectrum
Why Y(4260) is not seen in open charm decays?
… …
(4260)
Belle PRD77, (2008).

17. Opportunities for a better understanding the nature of Y(4260)
Theoretical prescriptions:
Hybrid
Tetraquark
Glueball
Hadronic molecules
Calculations done by various approaches:
Quark model
Hadron interaction with effective potentials
QCD sum rules
Lattice QCD
Cited 412 times!
See [hep-ph] for a recent review.

18. It could be an opportunity for understanding the mysterious Y(4260).
BESIII, arXiv: [hep-ex]
The mass of the charged charmonium-like structure Zc(3900) is about GeV.
It could be an opportunity for understanding the mysterious Y(4260).

19. The signature of Y(4260) could be revealed by the associated Zc near the DD* threshold!
D(1868) D
D0
Zc(3900), I,JP= 1, 1 D*
J/   D
M(Zc)  M(D) + M(D*) = GeV

20. The implementation of Weinberg theorem is possible 
The implementation of Weinberg theorem is possible
S-wave dominates in the production of Zc(3900)
S-wave dominates in DD* scattering to J/psi pi
The Zc decays into hc pi is not necessarily suppressed by the NR power counting  Zc
J/
Non-local pion radiation via triangle singularity kinematics: D1  D* D 
J/
Q. Wang, C. Hanhart, QZ, [hep-ph]

21. Singularity kinematics in ee J/D1    D* D  Zc
J/
J/
Wang, Hanhart and Zhao, work to appear in arXiv.

22. “prediction” from a molecular Y(4260) in J/ decay, 1303
“prediction” from a molecular Y(4260) in J/ decay, [hep-ph]
BESIII, [hep-ex]

23. Prediction for Y(4260)  hc  without  final state interactions
The threshold phenomena explains the significant heavy quark spin symmetry breaking (see talk by C. Hanhart and talk by E. Eichten).
Given the existence of a pole structure for Zc(3900), its production will be driven by the low-momentum DD* scattering apart from the cusp enhancement.
This may also explain that its production is not favored in the B decays.

24. Singularity kinematics in ee (nS) 
Two singularity regions by the BB* and B*B* thresholds can appear in the same c.m. energy in the (6S) decays. Two peaks are expected!

25. 3. Can we fit in some of the pieces of the jigsaw puzzle?

26. Given that Y(4260) is dominantly a DD1 molecule, a cusp structure will unavoidably appear in the invariant mass of J/psi pi at the DD* threshold due to the presence of a two-cut condition.
The cusp, however, seems to be insufficient to explain the relatively broad structure (~46 MeV). Thus, a charged charmonium with IG (JPC)=1 (1) is possible.
Similar phenomena occur to the Upsilon(5S)  Zb pi and Zb’pi.
Other implications of the molecular scenario are also made.

27. Thanks for your attention!

28. Quarkonium-like states near two-particle open threshold
Weinberg (1963); Morgan et al. (1992); Baru, Hanhart et al. (2003), ...
 Probability to find the hadronic molecule component in the physical state A

29. Cross section lineshape of
e+e  J/ 

30. Direct evidence for open charm effects in the cross section lineshape of
e+e  J/ 0
Wang, Liu, QZ, [hep-ph], PRD84, (2011)

31. In case that the open threshold coupled channels play a role, typical ways to include such an effect are via hadron loops in hadronic transitions
Q. Wang et al, PRD2012
X.-H. Liu et al, PRD81, (2010);
X. Liu et al, PRD81, (2010)
Y.J. Zhang et al, PRL(2009);
X. Liu, B. Zhang, X.Q. Li, PLB(2009)
Q. Wang et al. PRD(2012), PLB(2012)
“ puzzle”
G. Li and Q. Zhao, PRD(2011)074005
F.K. Guo and Ulf-G Meissner, PRL108(2012)112002
The mass shift in charmonium, E.Eichten et al., PRD17(1987)3090