Heavy hadron spectroscopy at Belle. Kenkichi Miyabayashi (Nara Women s University) Hadrons and Hadron Interactions in QCD Mar.

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1 Heavy hadron spectroscopy at Belle Kenkichi Miyabayashi (Nara Women s University) Hadrons and Hadron Interactions in QCD Mar. 2 nd 1

2 Outline Advantage with heavy flavors in hadron spectroscopy KEKB e + e - collider and Belle detector Variety of recorded reactions Quarkonium(-like) states X, Y and Z states in charmonium and bottomonium sectors Charm baryons Summary 2

3 Advantage of heavy flavors Light flavors (u,d,s) may mix; example η η Heavy, well-separated masses: relation between observed states and constituent quarks would be straight-forward. J/ψ, ψ(2s) e + e - or µ + µ -, (1S or 2S or 3S) µ + µ - : clean signature. 3

4 Variety of recorded reactions There are various processes to produce charmonium(-like) particles. In two-body B-decays, J PC =0 -+, 1, 1 ++ in factorization limit. Allowed/favored quantum numbers are different depending on production processes. γγ collision J PC =0 ±+, 2 ±+,3 ++ Initial state radiation J PC =1 4

5 KEKB/Belle : world highest luminosity as e + e - at region e + e - KEKB 8GeV 3.5GeV@ (4S) Belle High resolution 4π spectrometer with particle identification capability 5

6 Belle recorded more than 1 ab -1! 772M BB

7 Detector performance: great benefit Originally designed/constructed/operated for timedependent CP violation measurement in B system. 4π general purpose spectrometer with High momentum resolution, σ p /p = 0.3%@1GeV/c. Ability to detect γ down to 30 MeV. Good γ energy resolution, σ M =5MeV for π 0 γγ. Lepton identification capability, ε>0.9, fake<0.01. K/π/p separation capability, ε~0.9, fake<0.1. Excellent B decay vertex reconstruction, σ Δz =80µm. All these features led us to a lot of discoveries 7

8 First sensation was already 12 years ago; X(3872) ψ(2s) landmark B + J/ψ π + π - K + Look this system invariant mass. Very narrow peak is there, above DD threshold! Many things have been done, still actively discussed object. M ππll - M ll (GeV) Belle, 152M BB, PRL91,261801(2003) 8

9 More information about X(3872) PRD81, (2010) PRL110, (2013) X(3872) D 0 D *0 seen. Br(X(3872) D 0 D *0 ) is about Br(X(3872) J/ψ π + π - ) 10. Determined to be J PC =1 ++ (Belle, BaBar, CDF, LHCb) by J/ψ π + π - angular distribution. 9

10 LHCb visited radiative decay LHCb NPB886, 665(2014) LHCb M(J/ψ γ) (GeV) Taken from Polyakov Ivan s slides in Moriond QCD M(ψ(2S) γ) (GeV) 10

11 Admixture : most plausible interpretation for X(3872) X(3872) D ± D * D 0 D 0 * cc core Ar nucleus ~ 7 fm S.Takeuchi, K.Shimizu and M.Takizawa, arxiv: No signature for charged partner in J/ψ π + π 0. C=-1 partner in J/ψ η and χ c1 γ. most likely, isospin=0. disfavor tetraquark hypothesis. DD* molecule is mixing with the same J PC cc, χ c1 (2P) (yet unseen). can explain Br(X D 0 D *0 )/Br(X J/ψ π + π - ) is about 10. (pure molecule case, to be about 1000). pure molecule is too fragile to be produced in Tevatron/LHC. another χ c1 (2P) dominant state would become broad. Reaching such an interpretation is remarkable progress. 11

12 Additional recent knowledge PRD 90, (2014) B 0 X(3872) K - π + has been observed in X(3872) J/ψ π + π -. Fraction of B 0 X(3872) K *0 is small, different feature from ordinary J PC =1 ++ charmonium = χ c1. 12

13 Z(4430) + in ψ(2s)π ± final state 5.28GeV/c 2 Clear peak at 4.43 GeV/c 2 Reconstructing B ψ(2s) π ± K, M(ψ(2S) π ± ) is looked back. It is charged and contains cc, at least 4 constituents are necessary. PRL100,142001(2008) PRD 80, (2009) PRD 88, (2013) 13

14 Situation at current B-factories Belle : 660M BB PRL100, BaBar : 455M BB PRD79, Significant signal at Belle v.s. Only hint with 1.9σ at BaBar Belle s Dalitz plot analysis confirmed a resonance at 4430 MeV;PRD , (2009). Statistically, both are not contradicting with each other, but clear answer is to be given by higher statistics data. 14

15 LHCb confirmed Z(4430) + Fit with Z(4430) + Fit without Z(4430) + 4D fit(m(ψ(2s)π ± ), M(Kπ), cosθ ψ(2s), φ), PRL112, (2014) Z(4430) + interpretation is not as established as X(3872). 15

16 J/ψ π + system in B 0 J/ψπ + K - PRD90, (2014) One more charged state observed, J P =1 + 16

17 Surprise in bottomonium sector (ns) π + π - (n=1,2,3) production rate is 2 order of magnitude larger than (4s) state. PRL100,112001(2008) 17

18 Energy scan performed arxiv: S ππ 2S ππ (ns) π + π - also show peak around MeV. Different feature from around (4S) (10580 MeV). 3S ππ 18

19 Observation of h b (1P, 2P) in E cms =10880 MeV data MM(π + π - ) after background subtraction. PRL 108, (2012) 5.5σ 11.2σ (2S) (1S)ππ (3S) (1S)ππ M(h b (1P))= ± /-1.1 MeV M(h b (2P))= ± /-1.0 MeV R(h b (np)π + π - )/R( (2S) π + π - )=0.46± /-0.12, higher than expected. (For example, no h b (np) signal in (4S) data.) 19

20 Two charged states, Z b (10610) + and Z b (10650) + PRL108,122001(2012) (1S)π ± (2S) π ± (3S) π ± h b (1P)π ± H b (2P)π ± 20

21 Molecule picture works Decays to and h b can co-exist. Signature in B * B (*) partial recon. seen. A.E.Bondar et al., PRD84,054010(2011) J P =1 + is supported by Dalitz analysis. arxiv:

22 PRD88, (2013) Neutral Partner of Z b 0 First observation of ϒ(5S) ϒ (ns)π 0 π 0 Rates: about half of ϒ (ns)π + π Neutral partner in ϒ (ns)π 0 π 0 6.5σ stat. significance Mass 10609±4±4 MeV I G =1 +, first example to observe isospin partner among XYZ. 22

23 Back to charmonium(-like) by ISR Initial State Radiation BES III also confirmed the peak at 3885 MeV in (DD*) +. PRL110,252002(2013) PRL112,022001(2014) Y(4260) J/ψπ + π - Z(3895) + in J/ψπ + PRL110, (2013) 23

24 Charm baryon to check di-quark Thought to be a good place to check if di-quark is behaving as a good degree of freedom to form hadrons. One of the constituent quark is heavy, correlation between the remained light quarks would become clear. 24

25 Reconstructed states with Λ c Reconstruct Λ c pk - π + and add one pion. Σ c ++ Λ c+ π + PRD89,091102(2014) Σ c 0 Λ c+ π

26 Reconstructed states with Λ c (cont.) Select Σ c (2455) π to see Λ c+ π + π - Λ c (2880) + PRL98,262001(2007) Λ c (2880) + J=5/2 J=3/2 Λ c (2940) + M(Λ c+ π + π - ) [GeV] pion angular distribution 26

27 Reconstructed states with Λ c (cont. 2 ) PRD89,052003(2014) Σ c (2445) ++ Σ c (2520) ++ Λ c+ K - π + final state has been visited. Ξ c (2980) + Ξ c (3080) + Ξ c (3055) + Ξc (3080) + 27

28 Reconstructed states with Ξ c0 (cont.) Ξ c 0 is reconstructed in Ξ π +, pk - π + K - and ΛK - π + PRD89,052003(2014) Ξ c 0 π + has been visited. Ξ c 0 Ξ - π + Ξ c 0 ΛK - π + Ξ c 0 pk - π + K - 28

29 Reconstructed states with Ω c 0 PLB672,1(2009) Ω - ΛK - Ω c0 Ω - π + 29

30 Ω c0 (2770) Ω c 0 γ PLB672,1(2009) 30

31 States seen in ΛD mode 31

32 Note for charmed baryons For many states, mass and width were poorly known, B- factory results have been updating them. In Λ c+ π + K - case, only Ξ c (3080) + appears in Σ c (2445) ++ K - and Σ c (2520) ++ K -, while Ξ c (2980) + and Ξ c (3055) + appear only in Σ c (2445) ++ K -. Can resolving intermediate states help to see if di-quark is a good picture? For most of cases, branching fractions are also poorly known. To get information from the production rate, decay from higher states (feed-down) would become a problem Even PDG Br(Λ c pkπ), several underlying assumptions. New model-independent approach published from Belle. 32

33 Tag D (*)- p π + to get M miss PRL113,042002(2014) Detect only these 33

34 Then explicitly reconstruct pk - π + PRL113,042002(2014) PDG was 5.0±1.3% 34

35 Summary Because of superb detector performance with excellent accelerator luminosity, we got many exciting surprises, so far mainly quarkonium(-like). Some of those reached very plausible interpretation. X(3872) as admixture of molecule and charmonium(χ c1 (2P)) Z b (10610) + and Z b (10650) + as B*B (*) molecule. For the state close to the threshold, molecular state turned out to be playing important role. Extension to charmed baryons to test di-quark picture. Still unsettled interpretation for many states (ex. Z(4430) +, etc). Searches for new decay modes, partner states, attempt for J P determination with higher statistics data to cheer up relevant theorists to come up with convincing interpretation is a Belle II mission in hadron spectroscopy. 35