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
Outline
• Charmonium-like state
Y(4260) Y(4360)
• Y(5S) hidden-bottom dipion decays
Zb(10610) Zb(10650)
• Summary
2
Charmonium-like states
Y(4260) and Y(4360)
Dian-Yong Chen, Jun He and Xiang Liu
PRD83, 074012 (2011)
PRD83, 054021 (2011)
3
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)
4
Experimental status of Y(4260) and Y(4360)
PRL95, 142001 (2005)
Y(4260)
Spin-parity:
J
PC
=1
--
5
Y(4360)
Spin-parity:
PRL98, 212001 (2007)
J
PC
=1
--
PRL99, 142002 (2007)
M=4324±24 MeV
M=4361±9±9 MeV
Γ=172±33 MeV
Γ=74±15±10 MeV
6
Theoretical explanation
Exotic state:
• Charmonium hybrid
Y(4260)
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.
7
Conventional charmonium：
Y(4260)
• 4S-3D vector charmonium
Llanes-Estrada
3
• 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
8
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
9
Y(4260)
Y(4360)
ψ(4040)
ψ(4160)
D*D*
DD
?
PRL100,062001(2008)
DDπ
arXiv:0908.0231
DD*π
Λc+Λc–
Y(4660)
Y(4660)
DD*
PRD77,011103(2008)
PRL101,172001(2008)
if Ruds=2.285±0.03
PRL98, 092001 (2007)
ψ(4415)
ψ
y (4415)
Y(4260)
Y(4325)
Y(4360)
y (4160)
ψ(4160)
ψ (4040)
y
Y(4008)
ψ (3770)
y
R(s) = σ(e+e–→hadrons)/σ(e+e–→μ+μ–) – Ruds
Y(4008)
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
Durham Data Base
10
Non-resonant explanation for
Y(4260) and Y(4360)
The interference between Continuum and Resonance
11
Background
Y(4360)
Y(4260)
12
Can we reproduce the line shape of Y(4260) and Y(4360) in our model?
Five fitting parameters:
13
Numerical results for Y(4260)
D.Y. Chen, J. He and Xiang Liu, Phys.Rev.D83, 054021 (2011)
Y(4260)
Y(4008)
M=4008±40 MeV Г=226 ±44 MeV
Belle, Phys.Rev.Lett.99:182004 (2007)
14
Numerical results for Y(4360)
Dian-Yong Chen, Jun He and
Xiang Liu PRD83, 074012 (2011)
15
Y(5S) hidden-bottom
dipion decays
Zb(10610) and Zb(10650)
Dian-Yong Chen, Jun He, Xun-Qian. Li, Xiang Liu, PRD84, 074006 (2011)
Dian-Yong Chen, Xiang Liu, Shi-Lin Zhu, PRD84, 034002 (2011)
Dian-Yong Chen, Xiang Liu, PRD84, 094003 (2011)
Dian-Yong Chen, Xiang Liu, PRD84, 034032 (2011)
Dian-Yong Chen, Xiang Liu, Takayuki. Matsuki, PRD84, 074032 (2011)
Dian-Yong Chen, Xiang Liu, Takayuki. Matsuki, preparing
16
Dipion hidden-bottom decays of Y(5S)
Belle, PRL100, 112001
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
Belle, PRD82, 091106(R) (2010)
102
Puzzle existing in Y(5S)
dipion hidden-bottom
decays
17
Explanations of anomalous branching ratios of Y(5S)
hidden-bottom dipion decays
•
Rescattering mechanism
C. Meng, K.T. Chao PRD77, 074003 (2008)
PRD78, 034022 (2008)
PRD78, 074001 (2008)
Yu. A. Simonov JETP Lett. 87, 147 (2008)
H.W. Ke, Xiang Liu, X.Q. Li PRD82, 054030 (2010)
•
Bottom analogue of Y(4260)
s. Godfrey, S.L. Olsen arXiv:0801.3867
• Exotic structure-Tetraquark state near
Y(5S)
M. Karliner, H.J. Lipkin arXiv:0802.0649
A. Ali et al. PLB684, 28 (2010), PRL104, 162001 (2010)
18
Ali et al., PRL104, 162001
Chen, He, Li, Liu, PRD84, 074006 (2011)
Tetraquark explanation to Y(10870)
Indicate the
mistake in
Ali’s work
Propose
interference
effect
New puzzle!
19
Experiment status of two charged Zb
Belle Collaboration
arXiv:1105.4583
Zb(10610)
Zb(10650)
20
Zb structues and new puzzle
Chen, Liu, Zhu, PRD84, 054002 (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)?
21
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)
Predict BB* molecular state
Bondar, Garmash, Milstein, Mizuk, Voloshin, arXvi:1105.4473
Zhang, Huang, arXiv:1105.5472 QCD sum rule
Voloshin, arXiv:1105.5829 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:1105.5935
Guo, Cao, Zhou, Chen, arXiv:1106.2284
22
Theoretical explanation II- Mechanism
• D. V. Bugg, EPL96, 11002 (2011)
Cusp effect
• Yu. A. Simonov, arXiv: 1106.1522
•Dian-Yong Chen, Xiang Liu, PRD84, 094003 (2011)
Initial single pion emission (ISPE) mechanism
An underlying mechanism
without introducing exotic
explanation!
23
BB*
B*B*
Exp
BB
24
BB*
B*B*
BB
25
More predictions
Dian-Yong Chen, Xiang Liu, PRD84, 034032 (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
26
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
27
BESIII
Belle&BaBar
Belle II
28
Dian-Yong Chen, Xiang Liu, Phys. Rev. D84, 034032 (2011)
CLEO-c, PRL107, 041803 (2011)
e e  hc  @ 4170 MeV
 


e  e   J /   @ 4260 MeV
29
ISPE Mechanism
Bottomonium
Charmonium
PRD74,091103(R) (2006)
Strangeonium
PRL100,102003 (2008)
BES-II
M=2.175 GeV
Γ= 58 MeV
A series in flavor:
M=2.186 GeV
Γ= 65 MeV
Y (2175)    
 (1860)    
• Similar novel peak structures
• K*K : Sharp & Narrow
K*K* : Smooth& Broad
• More Experimental
Measurements (BESIII)
31
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
32
Thank you ！
33
A series in flavor:
ISPE Mechanism
Bottomonium
Charmonium
Strangeonium
34
PRD74,091103(R) (2006)
PRL100,102003 (2008)
BES-II
M=2.186 GeV
Γ= 65 MeV
M=2.175 GeV
Γ= 58 MeV
Summary of Mass of width
Process
M(GeV)
Γ(MeV)
BaBar(2006)
e  e   f 0 (980)
2.175
58
BES-II(2008)
J /  f 0 (980)
2.186
65
2.127
60
2.079
192
Belle(2009)
Belle(2009)
BES-II
e  e   
e  e     
*0
J /   K K *0
35
No Evidence of Y(2175)