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1 Charged Z’s at Ruslan Chistov (ITEP, Moscow) Representing the Belle Collaboration Quarkonium Working Group Workshop (Nara, NWU, December 2-5/2008) ●

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Presentation on theme: "1 Charged Z’s at Ruslan Chistov (ITEP, Moscow) Representing the Belle Collaboration Quarkonium Working Group Workshop (Nara, NWU, December 2-5/2008) ●"— Presentation transcript:

1 1 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 D0D0 D1*+D1*+ c d c u 

2 2 L > 870 fb -1 High Luminosity has permitted us to obtain unexpected non-trivial results on charm spectroscopy, particularly with charmonium in the final state. This has modified our understanding of known and predicted charmonia levels

3 3 Observed and predicted charmonia 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

4 4 The mechanisms of new particle production at B-factories 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 -   ISR Y(4260)  J/ψ  +  - Can charged Z be in principle produced here? Yes yet unknown (e + e -  X + Y - ??) No Since only neutrals can be produced

5 5 Observation of the first manifestly exotic state Z(4430) + at Belle (2007)

6 6 Z(4430) + at Belle Z(4430) + at Belle PRL 100, (2008) Study of BK + ’: ’l + l - and J/ +  - (M()>0.44 GeV); B-candidates inv. mass is kinematically constrained to m B (experim. resolution for M(‘ + )~2.5 MeV); Horizontal band K*(1430) K*(892) Study it

7 7 Z(4430) + at Belle Z(4430) + at Belle Total significance: 6.5 σ M = (4433±4  1) MeV  = ( ) MeV Br(B  KZ)xBr(Z   (2S)  + )= (4.1±1.0±1.3)·10 -5 PRL 100, (2008) Veto Fit: S-wave Breit-Wigner + Background with kinematic thresholds Cross-checks: Z(4430) + is present in both ’ subsamples

8 8 Z(4430) + at Belle Z(4430) + at Belle B +  Z + K s or B 0  Z - K + Z ±   (2S)  ± PRL 100, (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 , D.V.Bugg, ); - D*D 1 molecular state (X. Liu and Y.R. Liu, ); - radially excited tetraquark (L.Maiani, A.D.Polosa, V.Riquer, ); - baryonium state (C.F.Qiao, ); - hadro-charmonium (S.Dubinskiy,M.B.Voloshin, ); …

9 9 New charged Z’s decaying into  +  c1 Belle continued the study of other B(cc)  + K - decays PRD 78, (2008)

10 10 Study of BK -  +  c1 Similar selection, then look at DP: K*(892) K*(1430) Horizontal band Study it B-signal

11 11 Isobar Fit to entire Dalitz 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*’s below 1900 MeV

12 12 The fit results in DP slices without any Z’s: Confidence level of this fit: 3x A B C D A B C D

13 13 The fit results in DP slices with one Z: Confidence level of this fit: 0.5% Try an additional Z A B C D A B C D

14 14 The fit results in DP slices with two Z’s: Confidence level of this fit: 42% A B C D A B C D

15 15 Parameters of the EXOTIC new EXOTIC Z + 1,2  +  c1 states and Mass( +  c1 ) distribution are the same order as obtained for other, possibly exotic X,Y,Z states. No discrimination between J=0 or 1

16 16 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 

17 17 New results on Z(4430) + Full Dalitz Plot analysis of BK -  + ’ Data sample from original analysis is used The same fitting technique as in B  K  c1 is used

18 18 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

19 19 results on Z(4430) + from Dalitz plot fit results on Z(4430) + from Dalitz plot fit The results of the DP fit in its slices with Z: Confidence Level of the fit WITH Z(4430) + is 36% Significance of Z is 6.4σ NEW A B C D E A B C D E

20 20 Different fit models and the significance of Z(4430) + Significance of Z(4430) + in different fit models is always larger than 5σ

21 21 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 Z(4430) + from Dalitz plot fit Updated parameters of Z(4430) + from Dalitz plot fit

22 22 Summary of Belle results on manifestly exotic states 2007: Belle observed first charged charmoniumlike state, Z(4430) + decaying into ’ : Belle continued the study of BK(cc) decays and observed two new charged charmoniumlike states Z(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.

23 23 Back-up slides

24 24 K -  +  c1 Dalitz Plot Formalism The decay BK c1 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 BK c1 via 2-body intermediate res.R and c1 in hel. Angle dependent term: Signal event density Integrate over all angles; reconstruction efficiency is uniform over full angle ranges and interference terms between different  c1 helicity states are negligibly small.

25 25 M(K  ) description in B  K  +  ’ M(K  ) description in B  K  +  c1

26 26 M(K  ) description in B  K  +  ’ Cross-Check: angular distributions of the  c1 and J/  in B  K  +  c1 Data and predictions from the default fit model agree very well and little discrimination between spin 0 and 1

27 27 M(K  ) description in B  K  +  ’

28 28 Results of Dalitz Plot fit with two Z’s in B  K  +  ’ Significance of two Z’s over one Z is 3.9σ Preliminary

29 29 Dalitz Plot efficiency in B  K -  +  c1


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