Prospects for Hadron Physics. Roberto Mussa INFN Torino

Transcription

1 Prospects for Hadron Physics at Roberto Mussa INFN Torino Bormio 29/1/2014 1

2 Outline Bottomonium and Charmonium spectra Charmed+Beauty Mesons+Baryons Charged Bottomonia High Energy Scans at ~11 GeV ISR scans on Charmonium region Double Charmonium Hyperons and Dibaryons in Upsilon decays superkekb: collaboration, machine, detector 2

3 Data samples (units 106) Decays on Resonance Peak 160 Y(nS) Peak Running : CLEO-III 1,2,3S 2006: Belle 3,5S 2007: Belle 5S 2008: Babar 2,3S Belle 1,2,5S 2009: Belle 2,5S CLEO BABAR BELLE S Y(2,3S) Peak Bonus: Tagged 1S from Υ(2,3S) π+π-υ(1s) Y(4S) Peak Running e+e- Υ(nS) γisr PI+PI-Tagged Decays CLEO BABAR BELLE S σ(1s@10580) =19 pb σ(2s@10580) =17 pb σ(3s@10580) =29 pb (*) untagged γisr 3S 5S ISR untagged decays from 4S CLEO BABAR BELLE S 2S 3S 10 With 50 ab-1 at 4S: 0.95,0.85,1.45 G at 1,2,3S 5 0 2S 1S 3S 1S 3

4 Bottomonium amazing years for bottomonium spectroscopy: - Yb /Y(5S):observation of large dipion transitions to Y(1,2,3S) from 20 MeV above 5S peak - Discovery of ηb(2008) - Discovery of the triple cascade Yb Zb hb ηb * 4 parabottomonia * 2 charged bottomonia Zb Discovery (ATLAS) of χb(3p) 4

5 hb(1,2p) from Υ(5S) PRL108, Inclusive search : e+e- Υ(5S) π+π-+ Simultaneous discovery of hb(1,2p) New pathway to Y(1D) states 2S 1S 3S 1S A needle in a haystack? Residuals of the dipion recoil mass spectrum 5

6 hb(1,2p) from Υ(5S) PRL108, Significance after correcting for systematics effects: Masses very close to the COG of χ states, as expected from one gluon exchange. ΔMHF(1P) = 1.6±1.5 MeV/c ΔMHF(2P) = MeV/c Ratio of spin flip vs noflip dipion transitions totally unexpected from theory... 6

7 Charged Bottomonia : Zb's The two charged bottomonium states are observed in single pion recoil in 5 processes: Zb Z'b hb(1p) Zb Z'b hb(2p) - inclusive Y(5S) decays to hb(1,2p) - Dalitz plot of exclusive Y(5S) dipion transitions to Y(1,2,3S) Z'b Zb 7

8 Zb parameters PRL108,122001(2011) Belle discovered two charged bottomonium-like resonances: Z(10610) JP=1+ Zb Z(10650) Analysis of angular distributions suggests JP=1+ for both these states. Observation of Zb decays to BB* and B*B* is consistent with molecular nature of the charged bottomonia. (Voloshin, Bondar, et al) ArXiV: : Evidence of neutral partner of lower Zb in Yπ0 with 4.9 sigma significance 8

9 Zb BB*+BB*, B*B* ArXiV:

10 Belle-II: future prospects Neutral partners of Zb states proposed by Bondar et al. 10

11 Open questions: B K Zc PRD78 (2008) Ψ' Belle observed 3 charged peaks in B decays to charmonium + K cc=ψ' > Zc(4430) cc=χc1 > Zc(4050,4250) Never confirmed by Babar LHCb will have the fnal word? 11

12 Open questions: X(3872) γ ( J/ψ, ψ ') Babar [PRL 102 (2009), ]: X3872 γ J/ψ X3872 γ ψ' evidence of radiative decay to both J/ψ and ψ' : BR(X3872 γ ψ') = 3.4±1.4 BR(X3872 γ J/ψ) - disfavors the molecular model, - favors JPC=1++ - disfavors JPC= 2-+ Belle [PRL 102 (2009), ]: confrms radiative decay to J/ψ but not to ψ' Statistically limited: challenge for Belle-II Maybe possible at BES-III (poster by S.Braun) or LHCb 12

13 Rediscovery of ηb Phys.Rev.Lett. 109 (2012) Babar 2008: hb(1p) γηb (1S) χb(2p) γy(1s) γisry(1s) Y(3S) γηb (1S) hb(2p) γηb (1S) χb(1p) γy(1s) γisry(1s) Y(2S) γηb (1S) PRL 101,071801(2008) PRL 103,161801(2009) Sideband subtracted spectrum of ππγ recoil at the hb peaks. 13

14 Discovery of ηb(2s) Ldt = fb-1(5s) + 12 fb-1 (scan) PRL 109 (2012) hb(2p) γηb(2s) Sideband subtracted spectrum of ππγ recoil at the hb (2P) peak. 14

15 Parabottomonia vs theory ηb(2s) vs ηb(1s) PRL92,242001(2004) Lattice QCD PRD82,114502(2010) Godfrey-Isgur, PRD32,189 (1985) ηb(1s) 10 MeV discrepancy w/ earlier Babar and CLEO results Some tension with the most accurate NRQCD prediction, but very close to lattice QCD (Meinel) predictions. Spin averaged 1P-1S splitting seems not to depend on scale M(1P)-<M(1S)> =453.3±1.3 MeV/c2 15

16 Parabottomonia vs theory ηb(2s) vs ηb(1s) PRL92,242001(2004) Lattice QCD PRD82,114502(2010) Godfrey-Isgur, PRD32,189 (1985) 10 MeV discrepancy w/ earlier Babar and CLEO results: Skewed lineshape as in charmonium? Spin averaged 1P-1S splitting seems not to depend on scale: only 1% difference with charmonium: similarly, the tensor-vector splitting remains constant also in D,Ds. ηb(1s) M(1P) - <M(1S)> Charmonium 457.5±0.3 MeV/c2 Bottomonium 453.3±1.3 MeV/c2 16

17 Charmed and Beauty hadron spectra From Oka's talk at Hadron

18 Charmed and Beauty hadron spectra Ξc' 2646 Ξ'cav 2623 Ξ'b 5938? Ξ'b 5945 Ξc' 2577 missing 69 MeV ~150 MeV Ξc 2469 Ξb 5790 ~ 390 MeV Ds* 2112 Dsav MeV Ds 1968 Bsav 5403 Bs 5415 Bs MeV 18

19 Belle-II: future prospects Search for ηb(1s) γγ via exclusive channel: π+π-γ(γγ)!! NRQCD NNLL prediction: Penin et al., NP B699(2004),183 Γ(ηb(1S) γγ) γγ = 0.66±0.09 kev With Γ(ηb) = 10 MeV, BR(ηb(1S) γγ) γγ = 0.66*10-4 ~25 events with 1 ab-1 at Y(5S) Zb 19

20 Belle-II: future prospects Search for ηb(1s) γγ via exclusive channel: π+π-γ(γγ)!! NRQCD NNLL prediction: Penin et al., NP B699(2004),183 Γ(ηb(1S) γγ) γγ = 0.66±0.09 kev With Γ(ηb) = 10 MeV, BR(ηb(1S) γγ) γγ = 0.66*10-4 ~25 events with 1 ab-1 at Y(5S) Search for S=0 D-wave state via hb(2p) Zb Y(11D2) ηb(2s) 20

21 Belle-II: future prospects Search for ηb(1s) γγ via exclusive channel: π+π-γ(γγ)!! Y(6S) hb(3p) via Zbs states? hb(3p) γ ηb(3s)? NRQCD NNLL prediction: Penin et al., NP B699(2004),183 Γ(ηb(1S) γγ) γγ = 0.66±0.09 kev With Γ(ηb) = 10 MeV, BR(ηb(1S) γγ) γγ = 0.66*10-4 ~25 events with 1 ab-1 at Y(5S) Search for S=0 D-wave state via hb(2p) Zbs? Zb Y(11D2) ηb(2s) 21

22 Scans of the bb threshold region BaBar scans: points, 25/pb, 10.54,11.2 GeV Belle scans: - 61 points, 50/pb, GeV - 16 points, 1/fb, GeV BsBs BsBs* Bs*Bs* No evidence of Ali peak at BB* B*B* Future prospects at Belle-II: Full reconstruction of all B(*)B(*)+pion components 22

23 Scans of the cc threshold region: ISR DD D*D D*D* DDπ DD*π ΛcΛc 23

24 Full decomposition of R:Babar/Belle vs CLEO-c 24

25 Full decomposition of R:Babar/Belle vs CLEO-c 25

26 γ Bottomonium in 2013 Y(1S) γ +charmonium ey(1s) e+ cc NRQCD predictions All limits above th.predictions 6 BR(Y(1S) f )*10 90%CL UL Y(1S) γχc0 Y(1S) γχc1 Y(1S) γχc2 Y(1S) γηc + - Y(1S) γ X3872 γ π π J/ψ Y(1S) γ X3872 γ π+π-π0 J/ψ Y(1S) γ X3915 γ ωj/ψ Y(1S) γ Y4140 γ φj/ψ [K. T. Chao et al., hep-ph/ ] QCD QCD+QED QED PRD82(2010),051504R QCD 26

27 Search for H dibaryon Former observations by ARGUS and CLEO Z.Phys. C39 (1988) 177 Phys.Rev. D76 (2007) Inclusive production of (anti)deuteron in Y(1,2S) decays : - Enhanced (3x) production of low momentum hyperons in hadronic events from bottomonium decays w/respect to continuum. BELLE has exploited the Y(1,2S) record samples to search for the long sought H-dibaryon : (Jaffe, PRL38 (1977),195 ) A tightly bound tri-diquark, or a loosely bound S=2 hypernucleus? 27

28 Hyperon and dibaryon studies Many studies ongoing from Y(1,2S) decays, and from continuum: - pentaquark searches, - exclusive BR( ΛΛ+ n pions) - inclusive production of hyperons - ΛΛ and Ξ-p (+cc) correlations - antideuteron spectra (and more) 28

29 Search for ΛΛ threshold enhancements BELLE analysed ~50 exclusive channels with hyperon-antihyperon pairs + up to 6 light hadrons and with (0,1) neutral pion. Significance of the near threshold enhancement (in σ's) Both Y(1,2S) data and continuum were analysed. 29

30 Search for H dibaryon Recently studied by E522,STAR,ALICE Theory: recent lattice calculations HALQCD,NPLQCD Coll.: ~8 MeV binding Belle has searched for H dibaryon in the folllowing channels: - Λπp + ΛΛ(+cc) [PRL 110, (2013)] - Ξ p (+cc) [preliminary] 30

31 Double cc : J/ψ recoil method The double charmonium process was discovered by Belle by studying the momentum spectrum of J/psi. By plotting the mass of particles recoiling against the J/psi, Belle observed the peaks of charmonium C=0 states and discovered X(3940). This reaction challenges our understanding of perturbative QCD. Leading order prediction was O(0.1) the observed value. NLO calculations 'almost' solved the discrepancy. 31

32 Double cc : J/ψ+D recoil method Full reconstruction of one additional D meson and plot of the mass recoiling against the J/ψ+D system allowed to confrm X(3940) and fnd one more state at 4156 MeV. Future prospects at Belle-II: Full reconstruction of χc or ηc will allow to exploit the recoil technique and scan the charmonium(-like) C=-1 states. 32

33 Belle-II Collaboration 23 countries, 94 institutions, 560 collaborators 33

34 KEKB upgrade 34

35 New beam pipe 35

36 LER magnets installation 36

37 Belle-II: Detector 37

38 Belle-II: Vertex detectors 38

39 Belle-II: Barrel PID Challenging time resolution (100 ps) 39

40 Belle-II: Forward PID 40

41 Belle-II: Luminosity 41

42 SuperKEKB: Schedule 42

43 Summary In the last decade, B-factories have found most of the still missing pieces in bottomonium and charmonium spectra. S and P wave spectra below thresholds are almost complete: only the 2nd radial excitations (singlet 3S and 3P, doublet 3S) are missing. Many new questions arose from unexpected states across and above thresholds: Belle, Babar and BES-III are discovering a plethora of new states, the so called XYZ mesons, which require a spectroscopy with new degrees of freedom (tetraquarks, molecules, hybrids). Precise tests of NRQCD will require O(109) samples of Y(1,2,3S) decays or larger. Charged bottomonia (Zb states) have provided unique pathways to discover the missing spin singlet states. Their understanding is tightly coupled to the study of the charmonium-like counterparts (Zc states) observed by Belle and BES-III. Running at or above Y(5S) is compulsory for making further progress on this topic. Bottomonia provides also a unique environment for the study of hyperon-nucleon interactions, as their annihilations produce slow hyperons in large quantities, and are the only mesons which can produce nuclei (from deuteron to He-4). Possible studies include further searches for the long sought H-dibaryon. Belle-II is designed to run at 40 times higher luminosity, to accumulate 50 ab-1 of data by 2022, and will start physics running in

44 44