1. Charm Physics at Belle X,Y,Z states: just charmonia or exotics?
Jolanta Brodzicka (Krakow) for the Belle Collaboration
EXA2011, Vienna, September 2011

2. KEKB-Factory
KEK-B: e+(3.5GeV)  e-(8.0GeV), √s=m(4S)~10.58GeV
on-resonance e+e-(4S)BB σ~1.1nb (~109 BB)
continuum e+e-cc σ~1.3nb (~1.3109 XcYc)
 Also a charm factory
Data taking: June June 2010
Belle SuperKEKB will start in 2014

3. Charm topics D0-D0 mixing: governed by
In SM very suppressed: |x|,|y|~1% (with long distance effects)
Mixing modifies decay time: D0→K+π-, K+K-, π+π- lifetime measured,
D0→K0sπ+π- time-dependent Dalitz plot analysis,…
WA: x=(0.63±0.20)% y=(0.80±0.13)%, still no single-measurement observation
CP Violation:
In SM ≤0.1%, larger effects would mean New Physics
ACP measured for: D0→K+K-, π+π-, Ksη(‘), Ksπ0 D(s)+→Ksπ+, KsK+, φπ+, η(‘)π+
So far no evidence of CPV, but sensitivity ~0.2% at most
Decays: weak decays (like above),
(semi-)leptonic D0→πlν, Klν, Ds+→μν for form factors and decay constants,
radiative D10→D0γ for quark model tests, rare D0→l+l- for New Physics
Production of charmonia
Spectroscopy and strong decays of mesons, baryons and cc(-like) states
hadron charm physics

4. Charmonia n(2S+1)LJ hc c Many empty slots to fill
2 M(D)
recently measured
Quantum numbers
(4160)
(4415)
(4040)
(3770)
χc2′ ′
ηc′ ηc
J/
χc2
χc0 hc
χc1
n(2S+1)LJ
Many empty slots to fill
Expected broad states
decaying to DD, DD*, D*D*
All cc states predicted
below 2mD were observed
Good agreement with QCD
predictions
cc spectrum „cleaner” than uu/dd/ss → cc-like exotics easier to identify

5. Charmonium production in B-Factory

6. Particles discovered at Belle: history
2002: ηc’→KsKπ
D**: D*0(2308)→Dπ D1’(2420)→D*π
D*s0(2317)→Dsπ0 Ds1(2460)→Ds*π0
X(3872) →J/ψπ+π-
Y(3940)→J/ψω
Σc(2800) →Λc+π
X(3940)→D*D
χc2’→DD
Ξc(2980), Ξc(3077)→ΛcKπ
DsJ(2700) →D0K
Y family→J/ψπ+π- , ψ(2S)π+π-
X(4260)→D*D*
Z±(4430)→ψ(2S)π±
Z±(4051), Z±(4250)→χc1π±
2011: hb(1P),hb(2P) in Y(5S) →hbπ+π-
Zb±(10610), Zb±(10650)→Y(nS)π±, hbπ±
Will focus on charmonium-like XYZ
Are they exotic?
D*s0(2317) Ds1(2460)
Y(3940)
Σc(2800)0
Ξc(2980)
Ξc(3077)
DsJ(2700)
χc2’

7. XYZ charmonium-like states
Name
JPC
Γ (MeV)
Decay modes
Production
Exp’s
X(3872)
1++
2-+
<1.2
π+π-J/ ψ; γJ/ψ; D0D*0
B→KX,
pp→X+any
Belle/CDF/D0
BaBar/LHCb
X(3940)
0?+ 37
DD* (not DD, ωJ/ψ)
e+e-→J/ψX
Belle
Y(3940)
0,2++ 30
ωJ/ψ (not DD*)
B→KY, γγ→Y
Belle/BaBar
Y(4140)
??? 15
φJ/ψ
B→KY
CDF (not Belle)
X(4160)
~140
D*D* (not DD, DD*)
Y(4008)
1--
~220
π+π-J/ψ
e+e-→YγISR
Belle (not Babar)
Y(4260)
~80
π+π-J/ψ (not π+π-ψ’)
BaBar/CLEO/Belle
Y(4360)
~75
π+π-ψ’ (not π+π-J/ψ)
BaBar/Belle
Y(4660)
~50
π+π-ψ’;ΛcΛc (?)
Z±(4430)
???
~100
ψ(2S)π±
B→KZ
Belle (not Babar)
Z±(4050)
~80
χc1π±
Belle
Z±(4250)
~180

8. Conventional and exotics particles
Quark Model by Gell-Mann and Zweig (1964):
(qq) mesons and (qqq) baryons = conventional states
States more complex =exotics also predicted by potential models based on QCD
Phenomenology menu of cc-like exotics:
Molecule: Meson-antimeson loosely bound by pion exchange
Mass: ≈ sum of meson masses
Decay: dissociation into constituent mesons
Tetraquark: „Coloured” quarks tightly bound by gluon exchange
Decay: rearrange into „white” mesons → dissociation
Can have non-zero charge [cucd] and/or strangeness [cucs]
Hybrid: cc + constituent excited gluons
Can bear exotic JPC : 0+-, 1-+, 2+-…
Lowest cc-hybrids predicted by
Large partial widths for hadronic transitions (i.e. to ψππ, ψω…)
Hadrocharmonium: charmonium coated by excited light hadron matter q c π
D D(*) q c c g π c

9. X(3872), the most famous
PRL91, (2003)
Most cited Belle paper
X(3872)→J/ψπ+π- observed in B→X(3872)K by Belle in 2003
Confirmed by Babar, CDF, DØ, LHCb, CMS
Mass below or above D0D0*? (bound/virtual state?)
Peak at D0D*0 threshold is from X(3872)?
711/fb
N~170
arXiv:
M(J/ψπ+π-)
PRL103, (2009)
2.4/fb
N~6000
657M BB
D*→Dγ
D*→D0π0
M(D0D*0)
PRD81, (2010)

10. JPC of X(3872) M(π+π-)~ρ(770) in X(3872)→J/ψππ
arXiv:
M(π+π-)
__ S-wave
.... P-wave
M(π+π-)~ρ(770) in X(3872)→J/ψππ
 X(3872)→J/ψρ in S or P-wave  P-parity=+/-
Radiative X(3827)→J/ψγ decays  C-parity=+
But from Babar:
Angular analysis (Belle, CDF) JPC=1++ or 2-+
difficult to discriminate further
PRL107, (2011)
B+→XK+
711/fb
M(J/ψγ)
M(ψ’γ)
JPC= JPC= 2-+
PRL102, (2009)

11. Properties of X(3872)
Belle evidence of X(3872)→J/ψπ+π-π0, confirmed by Babar
 Large isospin violation. Unlikely for usual cc
No evidence of charged partner
X(3872)±→ J/ψπ±π0
arXiv: B± B0
M(J/ψω)
426/fb
BaBar: PRD71,031501(2007)
Belle: arXiv:
M(J/ψπ+π0)

12. What is X(3872)? charmonium? no good candidate
ηc2 (2-+) mass OK, JPC=2-+ supported by Babar’s X(3872)→J/ψω
X(3872)→ ηcππ should dominate
If X(3872) is cc, then why so narrow?
tetraquark? no evidence of Xu=[cu][cu] Xd=[cd][cd] neutral doublet
nor charged partner X±→J/ψπ±π0
DD* molecule? supported by large width of X(3872)→D0D*0
Large BR(X→ψ(2S)γ) from Babar is problematic.
Mixture of cc and DD* molecule?
Rulling out charmonia candidates...
ηc(3S) X(3872) too light and narrow
hc(2P) ruled out by angular analysis
χc1(2P) BR(X→J/ψγ) too small
ηc2(1D) BR(X→J/ψππ) too large
ψ2(1D) BR(X→χc1γ) too small
ψ3(1D) BR(X→χc2γ) too small
arXiv:

13. Y(3940)→J/ψω Y(3940)→J/ψω in B→ KY Y(3940)→J/ψω in γγ fusion
M(J/ψω)
X(3872) Y(3940)
426/fb
PRD82, (2010)
Y(3940)
253/fb
PRL 94, (2005)
M(J/ψω)
Γ(Y→J/ψω)>1MeV
Too large for cc
D*D* molecule
rescattering to J/ψω?
e+e- undetected
pt balance required
for final state
Partial wave analysis:
JP=0+,2+ prefered
694/fb
PRL104, (2010)
M(J/ψω)
eff vs W: drop at 3.9GeV. included in fit S-wave BW + 2G

14. 1-- Y family from ISR e+e-→J/ψπ+π-γISR and ψ(2S)π+π-γISR studied
ISR photon not required. ISR process identified
with missing mass and angular distribution
Study inv. mass of the final state hadrons
Y(4008), Y(4260), Y(4360), Y(4660) found
Not all of them can be usual charmonia,
only one empty 1-- slot left
s=E2CM-2ECMEISR
continuous ISR spectrum
 energy ‘scanning’
Produced states carry
JPC of photon
PRL99, (2007)
PRL 99, (2007)
550 fb-1
Y(4008) 7σ
Y(4260)
Y(4360)
Y(4660) 6
670 fb-1
M(J/ψπ+π-)
M(ψ’π+π-)
~80pb in Y(4260) and Y(4360) peaks

15. Y family, properties Study of e+e-→J/ψπ0π0 γISR (ISR photon required)
Motivation: study isospin relation
i.e. Y(4260)→J/ψπ0π0 wrt. Y(4260)→J/ψπ+π-
Large isospin violation would be exotic signature
Observed very little Y(4260) signal
Consistent with isospin expectation ψ’
Y(4260)
M(J/ψπ0π0)
M(J/ψπ0π0)
ψ’ S~630
Y(4260)
Preliminary 820/fb
~80pb in Y(4260) and Y(4360) peaks

16. 1-- Y→open charm? ? e+e-→open charm γISR
D*D*
DD*
(4040)
(4160)
Y(4008)
(4415)
Y(4660)
Y(4260)
Y(4350) DD
DDπ
Λc+Λc– ?
PRD77,011103(2008)
PRL100,062001(2008)
PRL98, (2007)
PRL101, (2008)
Y(4008), Y(4260), Y(4360), Y(4660)
are above open charm threshold but
don’t match peaks in D(*)D(*) cross-sections
90%CL limits for Y(4260):
Widths for Y→ψππ transition too large
for conventional charmonia
Y(4260) is DD1 molecule, ccg hybrid?
Then Y(4260)→DD*π should dominate
But no signal found
PRD79,092001(2009)
PRD80,091101(2009)
DD*π
Y(4260)
ψ(4415)
Y(4660) ?

17. Charged cc-like states: must be exotic!
Conventional
Molecule
Tetraquark
Hybrid
Hadrocharmonium
Z+(4430)→ψ’π+
Z+(4050) , Z+(4250)→χc1π+
Any Z+→J/ψπ+? Study ongoing
M2(ψ’π+) q c π
D D(*) q c
M(χc1π+) c g π c

18. Z(4430)±→ψ’π± was the first
PRL100, (2008)
PRD80, (2009)
Method: Dalitz-plot analysis of B→ψ’π+K
B→ψ’π+K amplitude: coherent sum of Breit-Wigner contributions
Models: all known K*→Kπ+ resonances only
all known K*→Kπ+ resonances and Z+→ψ’π+  favored by data
(significance: 6.4σ)
[cucd] tetraquark? neutral partner in ψ’π0 expected
D*D1(2420) molecule? should decay to D*D*π
M2(Kπ+)
M2(ψ’π+)
Z+(4430)
K2*(1430)
K*(890)
M2(ψ’π+) with K*’s vetoed
605/fb
–̶̶̶̶̶̶ –̶̶̶̶̶̶ Dalitz fit for model with K*’s only
–̶̶̶̶̶̶ –̶̶̶̶̶̶ Dalitz fit for model with K*’s and Z

19. Z(4430)±→ψ’π± in BaBar data?
Fits to efficiency corrected M(ψ’π+): no significant Z+(4430) signal
M(ψ’π+) from BaBar is statistically consistent with Belle data (χ2/ndf=54.7/58)
CDF result expected soon
Belle peak
position
PRD79, (2009)
M2(ψ’π+)

20. Any pattern in the XYZ puzzle?
Lots of non-cc 4GeV
Charged Z states must be exotic, neutral XY may be exotic
They have large hadronic transitions: unusal for conventional charmonia
No good candidates in cc spectrum or/and not enough empty slots
Close to the thresholds: what about threshold effects?
Mass ~ M(D+D*), M(Ds*+Ds*): molecules?
New
No single model can accomodate all XYZ states
Waiting for related predictions from Lattice QCD
Waiting for new mesurements and new data
„The finder of a new elementary particle used to be rewarded by a Nobel Prize,
but such a discovery now ought to be punished by a 10,000 dollar fine.”
Willis Lamb, Nobel Prize Lecture, 1955

21. Backup

22. cc (-like) state of art We have added a few new states…
Are they conventional cc? Do we understand them?
ηc(4S)
Y(3360), Y(3660)

23. Angular analysis of X(3872) at Belle

24. X(3872) backups M((2S)γ) M(J/γ) 0++ 1++ 1-- 2-+ 0.78/fb 3.6σ 424/fb
PRL98, (2007)
0.78/fb
3.6σ
424/fb
3.5σ
M((2S)γ)
M(J/γ)

25. Belle-BABAR comparison
Uncorrected data in the K* veto region
BABAR preliminary
Both Belle and BABAR data are re-binned (to calculate χ2) and side-band subtracted
The BABAR data are normalized (*1.18) to the Belle sample; Luminosity ratio is 1.46
The data distributions are statistically consistent (χ2=54.7/58)

26. for 1<M2(K-π+)<1.75GeV2
Two Z±→χc1π±
Dalitz-plot analysis of B0→χc1π+K- χc1 →J/ψγ with 657M BB
Dalitz plot models: known K*→Kπ only
K*’s + one Z →χc1π±
K*’s + two Z± states  favored by data
Significance: 5.7σ
PRD 78, (2008)
M2(χc1π+)
M2(K-π+ )
K2*(1430) K*(1680)
K*(892) K0*(1430) K3*(1780)
???
–̶̶̶̶̶̶ –̶̶̶̶̶̶ fit for model with K*’s
–̶̶̶̶̶̶ –̶̶̶̶̶̶ fit for double Z model
–̶̶̶̶̶̶ –̶̶̶̶̶̶ Z1 contribution
–̶̶̶̶̶̶ –̶̶̶̶̶̶ Z2 contribution
M(χc1π+)
for 1<M2(K-π+)<1.75GeV2

27. Zb±→Y(1,2,3S)ππ