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Charged Z’s at Charged Z’s at

Ruslan Chistov (ITEP, Moscow)Representing

the Belle Collaboration

Quarkonium Working Group Workshop (Nara, NWU, December 2-5/2008)

● Introduction ● Observation of Z(4430)+ +’ at Belle ● Observation of Z+

1,2+c1 at Belle

• Update of Z(4430)+ at Belle (NEW)● Summary

D0D1*+c

d c

u

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L> 870 fb-1

High Luminosity has permitted usto obtain unexpected non-trivial results on charm spectroscopy, particularly with charmonium in the final state.

This has modified our understanding ofknown and predicted charmonia levels

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Observed and predicted Observed and predicted charmoniacharmonia

Described well the observed spectrum of cc states

A number of unexpected exotic states above DD(*) thresholds that do not fit into available cc slots

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The mechanisms of new The mechanisms of new particle production at B-particle production at B-

factoriesfactories

From B-decays, e.g. B+X(3872)K+

In double charmonium production, e.g. e+e-

J/ψ X(3940)

In fusion, e.g. c(2S) or

Z(3930)

In radiative return, e.g. e+e- ISRY(4260) J/ψ +-

Can charged Zbe in principle produced here?

Yes

yet unknown(e+e-

X+Y- ??)

No

No

Since onlyneutrals can be produced

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Observation of the Observation of the first manifestly first manifestly

exotic state exotic state Z(4430)Z(4430)++ at Belle at Belle

(2007)(2007)

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Z(4430)Z(4430)++ at at BelleBelle

PRL 100, 142001 (2008)

Study of BK+’:

’l+l- and J/+- (M()>0.44 GeV);B-candidates inv. mass is kinematically constrained to mB

(experim. resolution for M(‘+)~2.5 MeV);

Horizontal band

K*(1430)

K*(892)Study it

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Z(4430)Z(4430)++ at at BelleBelle

Total significance: 6.5 σM = (4433±41) MeV= (44+17

-13+30

-11) MeV Br(BKZ)xBr(Z(2S)+)=(4.1±1.0±1.3)·10-5

PRL 100, 142001 (2008)

Veto Veto

Fit: S-wave Breit-Wigner + Background with kinematic thresholds

Cross-checks:Z(4430)+ is present in both ’ subsamples

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Z(4430)Z(4430)++ at at BelleBelle

B+Z+Ks or B0Z-K+

Z±(2S)±

PRL 100, 142001 (2008)

Charged, I=1

Cannot be a conventional charmonium or hybrid state

Should contain light quarks in addition to cc.

A variety of interpretations: - threshold effect (J.L.Rosner 0708.3496, D.V.Bugg, 0709.1254);- D*D1 molecular state (X. Liu and Y.R. Liu, 0711.0494);- radially excited tetraquark (L.Maiani, A.D.Polosa, V.Riquer, 0708.3997);- baryonium state (C.F.Qiao, 0709.4066 ); - hadro-charmonium (S.Dubinskiy,M.B.Voloshin,0803.2224); …

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New charged Z’s decaying New charged Z’s decaying into into ++c1c1

Belle continued the study of other B(cc) +K- decays

PRD 78, 072004 (2008)

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Study of BK-+c1

Similar selection, then look at DP:

K*(892) K*(1430)

Horizontal band

Study it

B-signal

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Isobar Fit to entire Dalitz Isobar Fit to entire Dalitz Plot:Plot:

+ K*(892) + K*(1410) + K*0(1430) + K*2(1430) + K*(1680) + K*3(1780) + (Z’s) + Interference

Efficiency over Dalitz Plot is included

All known K*’sbelow 1900 MeV

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The fit results in DP sliceswithout any Z’s:

Confidence level of this fit: 3x10-10

A B C DA B C D

A BA B

C DC D

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The fit results in DP sliceswith one Z:

Confidence level of this fit: 0.5%

Try an additional Z

A B C DA B C D

A BA B

C DC D

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The fit results in DP sliceswith two Z’s:

Confidence level of this fit: 42%

A B C DA B C D

A BA B

C DC D

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Parameters of the new EXOTICEXOTIC Z+

1,2 +c1 statesand Mass(+c1) distribution

are the same order as are the same order as obtained for obtained for other, possiblyother, possiblyexotic X,Y,Z states.exotic X,Y,Z states.

No discrimination between J=0 or 1

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Systematics and significances (incl. d.o.f.) from various fit models:

The worst case, but the param’s of this new K* are far from those for all known K*’s

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New results on Z(4430)New results on Z(4430)++

Full Dalitz Plot analysis of BFull Dalitz Plot analysis of BKK--++’ ’

Data sample from original analysis is used

The same fitting technique as in BKc1 is used

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Dalitz Plot slices: Fit without a Z resonance:CL=0.1%

Introduce Z

A B C D E

No K*3(1780) in the fit model: A B

C D

E

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results on Z(4430)results on Z(4430)++ from Dalitz plot from Dalitz plot fitfit

The results of the DP fit in its slices with Z:

Confidence Level of the fit WITH Z(4430)+ is 36%

Signifi

cance

of Z

is 6

.4σ

NEWNEW

A B

C D

E

A B C D E

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Different fit models and the significance of Z(4430)+

Significance of Z(4430)+ in different fit models

is always larger than 5σ

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Sum of 3 slices (K*’s veto)

Belle confirms the original result on Z(4430)+

Preliminary

Width is larger than original but uncertainties are large

Updated parameters of Updated parameters of Z(4430)Z(4430)++

from Dalitz plot fitfrom Dalitz plot fit

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Summary of Belle results on Summary of Belle results on manifestly exotic states manifestly exotic states

• 2007: Belle observed first charged charmoniumlikestate, Z(4430)+ decaying into ’+

• 2008: Belle continued the study of BK(cc) decays and observed two new charged charmoniumlike statesZ(4050)+ and Z(4250)+, decaying into +c1

• Update on Z(4430)+: Dalitz Plot analysis confirms original observation.The Z(4430)+ has a significance of 6.4σ.

These states have similar character: have non-zero electric charge and decay into ordinary charmonia and +.

The current options for their nature include tetraquark, molecular type states and hadro-charmonium.

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Back-up Back-up slidesslides

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K-+c1 Dalitz Plot Formalism

The decay BKc1 is described by 6 variables, M(c1), M(K), helicity angles c1, J/ and angles btw the production and decay planes c1, J/

Fitting function:

Amplitude for BKc1 via 2-bodyintermediate res.R and c1 in hel.

Angle dependent term:

Signal event density

Integrate over all angles; reconstruction efficiency is uniform over full angle ranges andinterference terms between different c1 helicity states are negligibly small.

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M(KM(K) description in B) description in BKK++’ ’ M(KM(K) description in B) description in BKK++c1c1

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M(KM(K) description in B) description in BKK++’ ’ Cross-Check: angular distributions Cross-Check: angular distributions

of the of the c1c1 and J/ and J/ in B in BKK++c1c1

Data and predictions from the default fit model agree very well and little discrimination between spin 0 and 1

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M(KM(K) description in B) description in BKK++’ ’

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Results of Dalitz Plot fit with two Results of Dalitz Plot fit with two Z’s in BZ’s in BKK++’ ’

Significance of two Z’s over one Z is 3.9σ

Preliminary

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Dalitz Plot efficiency in BDalitz Plot efficiency in BKK--

++c1c1