Heavy flavor meson(-like) spectroscopy at Belle/Belle II. Kenkichi Miyabayashi Nara Women s at Tokai 2015 Aug.

Transcription

1 Heavy flavor meson(-like) spectroscopy at Belle/Belle II Kenkichi Miyabayashi Nara Women s at Tokai 2015 Aug. 6 th 1

2 Outline Lessons from Belle experience XYZ sensations Current status and interpretations Quarkonium(-like) states Charm mesons Items to be tackled with Belle II Closing remarks 2

3 XYZ sensations at Belle PRL91,261801(2003) X(3872) J/ψπ + π - PRL110,252002(2013) Y(4260) J/ψπ + π - PRL100,142001(2008) Z(4430) + ψ(2s)π + M l+l-π+π- - M l+l- (GeV) PRL107,091803(2011) X(3872) J/ψ γ PRL110,252002(2013) Z(3900) + J/ψπ + Two Z b ± (ns)π ± PRL108,122001(2012) 3

4 What made it possible? From the experience of XYZ states, We need to have possibilities to access; Various production mechanisms Each physics process has preferable states. Interplay among several approaches is effective. Various decay modes Each hypothesis; other decay modes, partner states. Partner states have specific decay modes. 4

5 Variety of recorded reactions J PC =0 -+, 1, 1 ++ J PC =1 B decays Initial state radiation Double cc C=+1 γγ collisions J PC =0 ±+, 2 ±+,3 ++ Change CM energy Allowed/favored quantum numbers are different depending on production processes. 5

6 Belle detector CsI calorimeter Time Of Flight Aerogel Cerenkov S.C. solenoid 1.5T 3.5GeV e + 8GeV e - Silicon Vertex Detector K L µ system Central Drift Chamber High resolution, general purpose 4π spectrometer with particle-id.

7 Belle II Detector KL and muon detector: Resistive Plate Counter (barrel outer layers) Scintillator + WLSF + MPPC (end-caps, inner 2 barrel layers) EM Calorimeter: CsI(Tl), waveform sampling (baseline) (opt.) Pure CsI for end-caps electron (7GeV) Beryllium beam pipe Particle Identification Time-of-Propagation counter (barrel) Prox. focusing Aerogel RICH (fwd) 2cm diameter Vertex Detector 2 layers DEPFET + 4 layers DSSD Central Drift Chamber He(50%):C2H6(50%), Small cells, long lever arm, fast electronics positron (4GeV) Better or same performance under 20 7 beam background!

8 Variety of reactions; X(3915)=χ c0 (3915) In B ± J/ψωK ± decay In γγ J/ψω process B signal yield Y(3940)=X(3915) =χ c0 (3915) J/ψω M=3943±11(stat)±13(syst) MeV Γ=87±22(stat)±36(syst) MeV PRL94,182002(2005) X(3915)=χ c0 (3915) J/ψω N sig =49±14(stat)±4 events. M=3915±3(stat)±2(syst) MeV, Γ=17±10(stat)±3(syst) MeV J PC not yet determined. (still need confirmation for PDG 8 interpretation)

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

10 Admixture : most plausible interpretation for X(3872) X(3872) Ar nucleus D ± D * cc core ~ 7 fm D 0 D 0 * S.Takeuchi, K.Shimizu and M.Takizawa, arxiv: DD* component is coupled with the same J PC cc, χ c1 (2P) (unseen). can explain Br(X D 0 D *0 )/Br(X J/ψ π + π - ) is about 10. 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. 10

11 But no partner found No signature for Charged partner in J/ψ π + π 0. most likely, isospin=0. C=-1 partner in J/ψ η and χ c1 γ. disfavor tetraquark hypothesis. PTEP2014(2014)043C01 No 3872 J/ψ η mode PRL111,032001(2013) ψ 2 (1D) χ c1 γ mode No

12 What does it mean? If X(3872) is admixture of molecule and χ c1 (2P), its C-odd partner, J PC =1 +- state, is mixing with then not familiar with h c γ η c, η c in K S Kπ, etc. low branching fraction and S/N. J PC =1 +- is suppressed in two-body B decays. Higher statistics needed Belle II study item. 12

13 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 ± 13

14 Molecular 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:

15 PRD88, (2013) Partner states of Z b Z b (10610) 0 ϒ (2S)π 0 π 0 seen 6.5σ stat. significance I G =1 +, first isospin partner among XYZ. Partners may decay into χ bj (PRD86,014004(2012)). Z b χ bj π, Z b0 χ bj γ Br(χ bj (1,2,3S)γ) and γ efficiency are multiplied, signal yield may be lower one order of magnitude. Higher statistics needed. Various partner searches are a task for Belle II. 15

16 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. Confirmed by LHCb PRL112, (2014) PRL100,142001(2008) PRD 80, (2009) PRD 88, (2013) 16

17 Confirmation by LHCb 4D fit(m(ψ(2s)π ± ), M(Kπ), cosθ ψ(2s), φ), PRL112, (2014) Argand diagram gives a proof of resonance. Such approach will be possible to study other states with Belle II statistics only. 17

18 As for quarkonium(-like) states Molecular picture turned out to play important role near the threshold. X(3872) : D 0 D *0 and mixing with χ c1 (2P). Z b (10610) + : B B*, Z b (10650) + : B* B* Partner only found in Z b (10610) 0 (and Z(3900) 0 in CLEO) so far. Searches for other partners states need more data. Because of anticipated decay modes. Argand diagram approach only possible with Belle II statistics. 18

19 As for charmed mesons Various L=1 states have been accessed by continuum and B decays arxiv: , submitted to PRD B + D - D s + π + also visited to search for z ++ D s + π +, but no signature. U.L. given; D * s0(2317) + seen. 19

20 Competition with LHCb LHCb lumi (for possible & identified items) Accel. commissioning starts from early 2016 Novel idea (general search possible), quick publication

21 Closing remarks Quarkonium(-like) XYZ states Other decay modes and Partner searches need more data. Because of anticipated decay modes. Argand diagram only possible with Belle II statistics. As for charmed meson, various L=1 states visited, search for a doubly charged state attempted. Variety of recorded reactions and accessible decay modes continue to be exploited. All attempts with higher statistics data to give convincing and comprehensive understanding is a Belle II mission in hadron spectroscopy. 21

22 Backup slides 22

23 LHCb : Λ b J/ψ p K - b ccs transision, Cabbibo favored weak decay If Σ c D* molecule, story may be similar to the argument for X(3872).. CERN/LHCb collaboration arxiv: , submitted to PRL 23

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