1. Theoretical Progress on XYZ States
Dian-Yong Chen
Institute of Modern Physics, CAS
Research Center for Hadron and CSR Physics
Lanzhou University & Institute of Modern Physics of CAS
Collaborated with Xiang Liu, Jun He, Shi-Lin Zhu, Xue-Qian Li, T. Matsuki

2. Outline Charmonium-like state Y(4260) Y(4360)
Y(5S) hidden-bottom dipion decays
Zb(10610) Zb(10650)
Summary

3. Dian-Yong Chen, Jun He and Xiang Liu
Charmonium-like states Y(4260) and Y(4360)
Dian-Yong Chen, Jun He and Xiang Liu
PRD83, (2011)
PRD83, (2011)

4. According to the production mechanism, we can categorize these charmonium-like states X, Y, Z as four groups:
ISR process
Y(4260)
Y(4008)
Y(4360)
Y(4630)
Y(4660)

5. Experimental status of Y(4260) and Y(4360)
PRL95, (2005)
Y(4260)
Spin-parity: J =1 PC

6. Y(4360) Spin-parity: J =1 PRL98, 212001 (2007) PRL99, 142002 (2007)PC
PRL98, (2007)
PRL99, (2007)
M=4324±24 MeV
Γ=172±33 MeV
M=4361±9±9 MeV
Γ=74±15±10 MeV

7. Theoretical explanation
Exotic state:
Y(4260)
Charmonium hybrid
Zhu, Kou&Pene, Close&Page
Diquark-antidiquark state [cs][cs] Maiani&Riquer&Piccinini&Polosa, Ebert& Faustov & Galkin
Molecular state ( )
Liu&Zeng&Li, Yuan&Wang&Mo, Qiao, Ding, Torres&Khemchandani
&Gamermann&Oset, Close&Downum&Thomas
Charmonium hybrid state with strong coupling with DD1 and D D0
Kalashnikova &Nefediev
The lack of signal in certain channels also poses a serious challenge to a number of the explanations proposed in the framework of an exotic state.

8. 2 D1 state decay behavior  Eichten, Lane, Quigg
Conventional charmonium：
4S-3D vector charmonium
Llanes-Estrada
2 D1 state decay behavior 
Eichten, Lane, Quigg
Mass spectrum Y(4260) ≠charmonium
Segovia, Yasser, Entem, Fernandez
Screened potential Y(4260) =Ψ(4S)
Li, Chao 3

9. Conventional + exotic Y(4360) 3D charmonium or charmonium hybrid
Ding, Li&Chao
The radial excited state of Y(4260)
Qiao
Charmed baryonium
Cotugno&Faccini&Polosa&Sabelli
The vector hybrid charmonium with strong coupling with D*D0
Kalashnikova&Nefediev
molecular state Albuquerque & Nielsen
Close&Downum&Thomas

10. D*D*
DD*
ψ(4040)
ψ(4160)
Y(4008)
ψ(4415)
Y(4660)
Y(4260)
Y(4360) DD
DDπ
Λc+Λc– ?
PRD77,011103(2008)
PRL100,062001(2008)
PRL98, (2007)
PRL101,172001(2008)
DD*π
arXiv:
New
The main challenge of Y(4260) and Y(4360) as a conventional charmonium:
No evidence of Y(4260)/Y(4360) in the obtained open-charm process and R-value scan

11. Non-resonant explanation for Y(4260) and Y(4360)
The interference between Continuum and Resonance

12. Background
Y(4360) Y(4260)

13. Can we reproduce the line shape of Y(4260) and Y(4360) in our model?
Five fitting parameters:

14. Numerical results for Y(4260)
D.Y. Chen, J. He and Xiang Liu, Phys.Rev.D83, (2011)
Y(4260)
Y(4008)
M=4008±40 MeV Г=226 ±44 MeV
Belle, Phys.Rev.Lett.99: (2007)

15. Numerical results for Y(4360)
Dian-Yong Chen, Jun He and Xiang Liu PRD83, (2011)

16. Y(5S) hidden-bottom dipion decays Zb(10610) and Zb(10650)
Dian-Yong Chen, Jun He, Xun-Qian. Li, Xiang Liu, PRD84, (2011)
Dian-Yong Chen, Xiang Liu, Shi-Lin Zhu, PRD84, (2011)
Dian-Yong Chen, Xiang Liu, PRD84, (2011)
Dian-Yong Chen, Xiang Liu, PRD84, (2011)
Dian-Yong Chen, Xiang Liu, Takayuki. Matsuki, PRD84, (2011)
Dian-Yong Chen, Xiang Liu, Takayuki. Matsuki, preparing

17. Dipion hidden-bottom decays of Y(5S)
Belle, PRL100,
Belle, PRD82, (R) (2010)
Decay channel MeV
Y(5S)Y(1S)π+π-
0.59
Y(5S)Y(2S) π+π-
0.85
Y(5S)Y(3S) π+π-
0.52
Y(2S)Y(1S) π+π-
0.006
Y(3S)Y(1S) π+π-
0.0009
Y(4S)Y(1S) π+π-
0.0019
102
Puzzle existing in Y(5S) dipion hidden-bottom decays

18. Rescattering mechanism
Explanations of anomalous branching ratios of Y(5S) hidden-bottom dipion decays
Rescattering mechanism
C. Meng, K.T. Chao PRD77, (2008)
PRD78, (2008)
PRD78, (2008)
Yu. A. Simonov JETP Lett. 87, 147 (2008)
H.W. Ke, Xiang Liu, X.Q. Li PRD82, (2010)
Bottom analogue of Y(4260)
s. Godfrey, S.L. Olsen arXiv:
Exotic structure-Tetraquark state near Y(5S)
M. Karliner, H.J. Lipkin arXiv:
A. Ali et al. PLB684, 28 (2010), PRL104, (2010)

19. Indicate the mistake in Ali’s work Propose interference effect
Ali et al., PRL104,
Chen, He, Li, Liu, PRD84, (2011)
Tetraquark explanation to Y(10870)
Indicate the mistake in Ali’s work
Propose interference effect
New puzzle!

20. Experiment status of two charged Zb
Belle Collaboration
arXiv:
Zb(10610)
Zb(10650)

21. Zb structues and new puzzle
Chen, Liu, Zhu, PRD84, (2011)
Two newly observed Zb structures play important role to solve “new puzzle” in Y(5S)Y(2S)π+π- decay
Question: what is the source to generate Zb(10610) and Zb(10650)?

22. Theoretical explanation I- Exotic strucutes
S-wave BB* and B*B* molecular states
Liu, Xiang Liu,Deng, Zhu, EPJC56, 63 (2008)
Xiang Liu, Luo, Liu, Zhu, EPJC61, 411 (2009)
Bondar, Garmash, Milstein, Mizuk, Voloshin, arXvi:
Zhang, Huang, arXiv: QCD sum rule
Voloshin, arXiv: Radiative decays
Cleven, Guo, Hanhart, Meissner, EPJA, 47, 120 (2011)
Sun, He, Xiang Liu, Luo, Zhu, PRD84:054002,2011
One-Boson-Exchange model
Tetraquark state
Yang, Ping, Deng, Zong, arXiv:
Guo, Cao, Zhou, Chen, arXiv:
Predict BB* molecular state

23. Theoretical explanation II- Mechanism
D. V. Bugg, EPL96, (2011) Cusp effect
Yu. A. Simonov, arXiv:
Dian-Yong Chen, Xiang Liu, PRD84, (2011)
Initial single pion emission (ISPE) mechanism
An underlying mechanism without introducing exotic explanation!

24. BB* BB
Exp
B*B*

25. BB*
B*B* BB

26. Dian-Yong Chen, Xiang Liu, PRD84, 034032 (2011)
More predictions
Dian-Yong Chen, Xiang Liu, PRD84, (2011)
If the ISPE mechanism is a universal mechanism in heavy quarkonium dipion decays, we naturally extend the ISPE mechanism to study the hidden-charm dipion decays of higher charmonia or higher bottomonia

27. Dian-Yong Chen, Xiang Liu, Takayuki. Matsuki, PRD84, 074032 (2011)
Predicted charged bottomonium-like structures near BB* and B*B* threshold.
Belle II and SuperB

28. BESIII
Belle&BaBar
Belle II

29. Dian-Yong Chen, Xiang Liu, Phys. Rev. D84, 034032 (2011)
CLEO-c, PRL107, (2011)

30. A series in flavor: ISPE Mechanism Bottomonium Charmonium Strangeonium
M=2.175 GeV
Γ= 58 MeV
PRD74,091103(R) (2006)
PRL100, (2008)
BES-II
M=2.186 GeV
Γ= 65 MeV
A series in flavor:

31. Similar novel peak structures
K*K : Sharp & Narrow
K*K* : Smooth& Broad
More Experimental
Measurements (BESIII)

32. Summary Non-resonant explanation to Y(4260) and Y(4360)
Charged Zb(10610) and Zb(10650)
Mechanism：ISPE mechanism
Extend to Charmonium, Strangeonium
More efforts theory+experiment
Belle-II, BESIII, LHCb, SuperB, PANDA

33. Thank you ！

34. A series in flavor: ISPE Mechanism Bottomonium Charmonium Strangeonium34

35. Summary of Mass of width
M=2.175 GeV
Γ= 58 MeV
PRD74,091103(R) (2006)
PRL100, (2008)
BES-II
M=2.186 GeV
Γ= 65 MeV
Summary of Mass of width
Process
M(GeV)
Γ(MeV)
BaBar(2006)
2.175 58
BES-II(2008)
2.186 65
Belle(2009)
2.127 60
2.079
192
BES-II
No Evidence of Y(2175) 35