Recent XYZ results from Belle

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1 Recent XYZ results from Belle Changzheng Yuan IHEP, Beijing Mini-workshop on XYZ, IHEP, Beijing May 11, 2015

2 The Belle experiment SCC RF(HER) Belle detector World record: L = 2.1 x /cm 2 /sec ARES(LER) 8 x 3.5 GeV 22 mrad crossing /fb Ares RF cavity e + source KEKB Mt. Tsukuba Belle The KEKB Collider ~ 1 km in diameter 2

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4 outline Recently released XYZ results Ongoing analyses on XYZ Prospects at Belle II Summary 4

5 The X(3872) Mass: Very close to D 0 D *0 threshold Width: Very narrow, < 1.2 MeV J PC =1 ++ Production in pp/pp collison rate similar to charmonia In B decays KX / K*X vs. charmonium [Belle, next pages] Y(4260) +X(3872) [from BESIII] Decay BR: open charm ~ 50%, charmonium~o(%) Nature (very likely exotic) Loosely D 0 D *0 bound state (like deuteron?)? Mixture of excited c1 and D 0 D *0 bound state? Belle, /fb M( J/ ) M(J/ ) [GeV] Many other possibilities (if it is not c1, where is c1?) 5

6 B X(3872)K PRD84, (2011) 711 fb -1 N s =151±15 B ± XK ± N s =21.0± B 0 XK 0 6

7 More information on X(3872) arxiv: (Never published!) PRD91,051101(R) (2015) 7

8 B X(3872)K 2D-fit to and M(J/ + - ) B 0 X(3872)K + - PRD91,051101(R) (2015) 116±19 X(3872) 7.0σ B + X(3872)K S + 35±10 X(3872) 3.7σ 8

9 B X(3872)K B 0 X(3872)K + - Fit K invariant mass with K*, K* 2 and Nonresonance terms from signal MC B 0 (2S)K + - B(B 0 (2S)K * ) = ( )x10-4 9

10 X-like states decaying to c modes arxiv:

11 X-like states decaying to c modes 11 arxiv:

12 X-like states decaying to c modes 12 arxiv:

13 Z(3900) 0 / Z(4020) 0 / X(3915) η c modes arxiv:

14 e + e - γx b γωϒ(1s) PRL 113, (2014) The X(3872) counterpart in the bottomonium sector X b, NOT observed decay channel π + π - ϒ(1S). As X b is above ωϒ(1s) threshold, this Isospin-conserving process should be more promising. [PRD88, ]. Reflection of e + e - ωχ bj PLB 727, 57 (2013). Assuming X b narrow, the product branching fraction : Br(ϒ(5S) γx b )Br(X b ωϒ(1s)) varies from to between and GeV/c 2. 14

15 e + e - π + π - π 0 χ bj at GeV Motivations: Heavy quarkonia hadronic transition : QCD multipole expansion (QCDME) model. [Y. P Kuang, Front Phys. China 1, 19 (2006)] For ϒ(5S) resonance peak: The anomalously large width :e + e - π + π - ϒ(ns) [Belle PRL 100, ] and e + e - π + π - h b (ns) [PRL 108, ]. Z b (10610) ± and Z b (10650) ± [PRL 108, ]. Search for hadronic transition : ϒ(5S) π + π - π 0 χ bj 15

16 e + e - π + π - π 0 χ bj 118 fb -1 ϒ(5S) data sample χ bj γϒ(1s) PRL 113, (2014) 12σ 5.9σ The same order as e + e - π + π - ϒ(nS). [PRL 100, ]. Hadronic loop effect? Assuming all events decay from ϒ(5S). [arxiv: ] Born cross section: Product BF : σ(e + e - π 0 π + π - χ b0 ) < 3.4 (pb) at 90% C.L. BF(ϒ(5S) π 0 π + π - χ b0 ) < at 90% C.L. σ(e + e - π 0 π + π - χ b1 ) = 0.98±0.12±0.12 (pb) BF(ϒ(5S) π 0 π + π - χ b1 ) =(2.02±0.25±0.25) 10-3 σ(e + e - π 0 π + π - χ b2 ) = 0.62±0.14±0.08 (pb) BF(ϒ(5S) π 0 π + π - χ b2 ) =(1.27±0.29±0.16)

17 e + e - π + π - π 0 χ bj 2D fit to scatter plot of M(π + π - π 0 ) vs M(γϒ(1S)). PRL 113, (2014) π + π - π 0 invariant mass distribution: ω signal An enhancement in higher M(π + π - π 0 ) 17

18 e + e - ωχ bj ω signal region. 12σ Χ b2 : 3.5σ Born cross section: σ(e + e - ωχ b0 ) < 1.9 (pb) at 90% C.L. σ(e + e - ωχ b1 ) = 0.76±0.11±0.11 (pb) σ(e + e - ωχ b2 ) = 0.29±0.11±0.08 (pb) 18

19 e + e - (π + π - π 0 ) non-ω χ bj PRL 113, (2014) The χ bj candidates out of ω signal region. Possible cascade decay from ϒ(5S) πz b πρχ bj [arxiv: ] The interpretation is currently limited. Χ b1 : 4.9σ Χ b2 : 3.1σ Born cross section: σ(e + e - (π + π - π 0 ) non-ω χ b0 ) < 2.3 (pb) at 90% C.L. σ(e + e - (π + π - π 0 ) non-ω χ b1 ) = 0.25±0.07±0.06 (pb) σ(e + e - (π + π - π 0 ) non-ω χ b2 ) = 0.30±0.11±0.14 (pb) 19

20 The Y states PRL99, /fb PRL99, /fb PRL98, /fb PRL95, /fb Y(4008) Y(4260) Y(4360) Y(4660) Y(4630) Above DD threshold, decay to open charm? PRL101, /fb M( c+ c- ) 20

21 e + e J/ from ISR PRL110, (2013) Still observed two resonances, Y(4008) and Y(4260), agrees with Belle s previous results. R 1 =Y(4008) R 2 =Y(4260) 1. Fit with two coherent resonances BW 1 +BW 2 *exp(if) 2 +bkg. 2. Mass of Y(4008) is lower than before 3. Fit quality: 2 /ndf=101/84, confidence level is 9.3% 21

22 e + e J/ from ISR PRL110, (2013) M 2 ( ) vs. M 2 ( J/ ) for 4.15<M( J/ ) <4.45 GeV (inset) Background events in J/ -mass sidebands Structures both in and J/ systems 689 events in J/ signal region, purity~80% 22 22

23 Z(3895) + observed in two experiments! Belle with ISR: PRL110, BESIII at GeV: PRL110, M = MeV = MeV events >5.2 M = MeV = MeV events >8 23

24 Confirmed with CLEOc data! CLEOc data at 4.17 GeV: arxiv: , PLB727, 366 (2013) BESIII Belle M = MeV = MeV events

25 e + e (2S) via ISR ( J/ or ) + no extra tracks detection of ISR is not required 980 fb -1 Clear signal of missed massless particle (M rec2 ( )~0) Two significant clusters: Y(4360)+Y(4660); a few events at Y(4260) Polar angle distribution agrees well with ISR expectation Combinatorial background estimated by sidebands Bkgs from real ( ) non ISR or X non are negligibly small Belle: arxiv:

26 Fit with Two BWs Belle: arxiv: J/ 26

27 Fit with Three BWs J/ + Belle: arxiv:

28 Fit with Three BWs J/ + Belle: arxiv: Significance of Y(4260) is 2.4 Affect the parameters of Y(4360) and Y(4660) significantly! 28

29 M( + - ) distributions J/ Y(4360) +f 0 (980) Y(4660)

30 Zc states from Y(4360) decays? J/ Belle: arxiv:

31 Z c (4050) arxiv: M(Z c ) = 4054 ± 3 ± 1 MeV/c 2 Γ = 45 ± 11 ± 6 MeV Significance: >3.5 An unbinned maximumlikelihood fit is performed on the distribution of M max (π ± ψ(2s)), the maximum of M(π + ψ(2s)) and M(π ψ(2s)), simultaneously with both modes. 31

32 No significant Zc in Y(4660) decays! J/ Belle: arxiv:

33 e + e - K + K - J/ via ISR Event selections are almost the same as in Phys. Rev. D 77, (R) (2008) Shaded hist.: J/ mass sidebands Y(4260) 980fb -1 +one resonance. Fit with (4415) 2 /ndf=30/11 M= MeV = MeV 4-6 GeV: 213 events 35 bkg, signal 7.8% sys. error was not included. PRD 89,072015(2014) 33

34 Search for Z cs KJ/ states PRD 89,072015(2014) Large data samples at BelleII are needed to understand KJ/ and KKJ/ structures! No evident structure in K ± J/ mass distribution under current statistics 34

35 30k signal evts PWA of B J/ K 4D PWA Resonances: all K*s and Zc(4430) Search for additional Zc states sideband eff. Belle: PRD 90, (2014) 35

36 PWA of B J/ K Zc(4200)! Belle:, PRD 90, (2014) 36

37 PWA of B J/ K A JP=1+ charged charmoniumlike state Zc(4200) is observed in its decay to J/! Belle:, PRD 90, (2014) 37

38 PWA of B J/ K 4.0 evidence for Z c (4430) J/! No significant B Z c (3900)K signal observed! Belle:, PRD 90, (2014) 38

39 PWA of B J/ K New state Z c (4200)! Very wide! 4.0 evidence for Z c (4430) J/! No significant B Z c (3900)K signal observed! Belle:, PRD 90, (2014) 39

40 IJMPA 29, (2014) Many Z c ± states now We are eager to know their nature! 40

41 2. Ongoing analyses on XYZ 41

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44 Blind analysis is on going Check the expectation before open the signal window in data Using two (anti-)charmed mesons, we calculate recoil mass 44

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46 3. Prospects at BelleII 46

47 SuperKEKB collider e + 4GeV 3.6 A Belle II Colliding bunches New beam pipe & bellows e - 7GeV 2.6 A SuperKEKB New IR New superconducting /permanent final focusing quads near the IP Replace short dipoles with longer ones (LER) Redesign the lattices of HER & LER to squeeze the emittance Low emittance positrons to inject Damping ring Add / modify RF systems for higher beam current Positron source New positron target / capture section TiN-coated beam pipe with antechambers Low emittance gun Low emittance electrons to inject Target: L = 8x10 35 /cm 2 /s 47

48 Belle II is coming ISR produces events at all CM energies BESIII can reach At 4.26 GeV for + - J/ BESIII = 46% Belle = 10% 48

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50 Summary Lots of results on XYZ states Nature yet to understand Belle is still producing results with 1/ab data Belle II will collect 50/ab data to improve the analyses Thanks a lot! 50

51 The end 51