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New Results on Hadron Spectroscopy (Experimental Review)

New Results on Hadron Spectroscopy (Experimental Review). Shan JIN Institute of High Energy Physics (IHEP) Chinese Academy of Sciences jins@mail.ihep.ac.cn August 20, 2004 ICHEP 2004, Beijing. Multi-quark State, Glueball and Hybrid. Hadrons consist of 2 or 3 quarks ：

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New Results on Hadron Spectroscopy (Experimental Review)

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  1. New Results on Hadron Spectroscopy (Experimental Review) Shan JIN Institute of High Energy Physics (IHEP) Chinese Academy of Sciences jins@mail.ihep.ac.cn August 20, 2004 ICHEP 2004, Beijing

  2. Multi-quark State, Glueball and Hybrid • Hadrons consist of 2 or 3 quarks： Naive Quark Model： • New forms of hadrons: • Multi-quark states：Number of quarks >＝ 4 • Hybrids：qqg，qqqg … • Glueballs：gg， ggg … Meson（ qq ） Baryon（q q q）

  3. Multi-quark states, glueballs and hybrids have been searched for experimentally for a very long time, but none is established.However, during the past one year, a lot of surprising experimental evidences showed the existence of hadrons that cannot (easily) be explained in the conventional quark model.

  4. There are so many exciting unexpected new observations as well as many negative search results that I will not be able to cover many “conventional” topics, such as charm baryons, charmonium production… I would deeply apologize to those experiments who contribute these beautiful results to the conference.

  5. Outline • Multi-quark candidates: • Pentaquarks • X(3872) • DsJ(2632) • Resonant structures near mass thresholds and J/ mass thresholds. • Light scalar mesons: • σ, κ, f0(980), f0(1370), f0(1500), f0(1710), f0(1790) • Other interesting results from BES and CLEO-c

  6. Observations of pentaquarks

  7. Θ+(1540) • First evidence of pentaquark was presented by LEPS in the process : Nevent= 19 +/- 2.8 Significance: ~ 4.6 σ • Minimum quark content: uudds Its mass and width are consistent with chiral soliton model prediction. LEPS at 90% CL MnK+

  8. CLAS CLAS M(nK+) M(nK+)

  9. SAPHIR M(nK+) (fit)

  10. Inclusive γ*- production HERMES M(pKs)

  11. RΛ ~ 0.04 Assuming the production rate of Λ*(1520) is 5 times smaller than Λ, I estimated: RΛ*(1520) ~ 0.2 ZEUS Fragmentation (fit) M(pKs)

  12. DIANA Asratyan et al. - induced M(pKs) M(pKs)

  13. M(pKs) M(pKs)

  14. Pentaquarks at JINR How many pentaquarks did they see? M(nK+)

  15. MΘ (LEPS) F. Close and Q. Zhao, hep-ph/0404075

  16. ΓΘ • PDG 04: (R.N. Cahn, G.H.Trilling, PR D69 011501R, based on the production cross-section estimation from DIANA data,σR=ABiBfΓ) • Consistent with other estimation of the upper limit on the width based on K+N partial wave reanalysis ( < 1 MeV ) Why the width is so narrow seems very hard to understand.

  17. Isospin of Θ+(1540) • No Θ++was observed by SAPHIR, HERMES or other experiments.  Θ+ is an isoscalar

  18. Ξ--(1862) NA49 pp collision at Ecm=17.2GeV • Also evidence for Ξ0(1862) ( I = 3/2 )

  19. Θc(3099) DIS (Q2 > 1GeV2) • Minimum quark content:uuddc Poisson Prob.

  20. Negative search results on pentaquarks

  21. BES Upper limits @ 90% C.L. BR ((2S)    (KSp)(K-n) + (KSp)(K+n))< 0.84X10-5 BR (J/    (KSp)(K-n) + (KSp)(K+n)) < 1.1 X10-5 y(2S) J/y RΛ*(1520) < ?

  22. ALEPH • No evidence forΘ+(1540), Ξ--(1862),Ξ0(1862) , Θc(3100) in Z decays M(pKs)

  23. ALEPH Limits at 95% C.L. Also no evidence for Θ+(1540), Θ++(1540) at DELPHI

  24. L3 • No evidence for Θ+(1540) in two photon collisions.

  25. CDF • No evidence ofΘ+(1540), Ξ--(1862),Ξ0(1862) or Θc(3100)observed at CDF. Θ+(1540) M(pKs) Θc(3100)

  26. HERA-B No evidence of Θ+(1540), Ξ--(1862),Ξ0(1862) at HERA-B (proton-nucleus collisions at ) M(pKs)

  27. ZEUS • Θc(3099) was not observed at ZEUS in a data sample which is 1.7 times of the H1 data sample. 95% C.L. upper limit: Inconsistent with H1:~0.01 More quantitative comparisons require detector efficiency corrections. M(D*p)

  28. BaBar • No evidence ofΘ+(1540), Ξ--(1862) or other possible pentaquarks was observed at BaBar. Upper limits were set. • RΛ*(1520) < ~ 0.01 @ 90 % CL

  29. Belle • Belle did not see Θ+(1540): RΛ*(1520) < 0.02 @ 90 % CL • Θc(3100) was not seen either. 155fb-1 pK- (1520) pKS nothing m(GeV)

  30. Inconsistencies (I) • Width of Θ+(1540) • Two “positive” experiments: HERMES: ΓΘ= 17 9  2 MeV ZEUS: ΓΘ= 8  4 MeV • K+N PWA results indicates ΓΘ < 1 MeV • Mass of Θ+(1540)

  31. MΘ (LEPS)

  32. Inconsistencies (II) • Production rate (e.g. for Θ+(1540) ) • “Positive” experiments: SAPHIR:RΛ*(1520) ~ 0.3 HERMES: RΛ*(1520) ~ 1.6~3.5 ZEUS: RΛ*(1520) ~ 0.2 ( I estimated from RΛ ~ 0.04 ) SVD-2: RΛ*(1520) > 0.2 ( estimated by SPHINX, hep-ex/0407026) • “Negative” experiments: ALEPH: RΛ*(1520) < 0.1 BaBar: RΛ*(1520) < ~ 0.01 Belle: <0.02 HERA-B: RΛ*(1520) < 0.027~0.16 SPHINX: RΛ*(1520) < 0.02

  33. The “negative” experiments have much larger statistics, also are at relatively higher energies (but Babar and Belle are at low energy). • Pentaquarks do not exist, or • Pentaquarks have very exotic production mechanism. via N*? Then why N* has much higher production rate at low energy? • Looking forward to more experimental results at low energy with high statistics, especially those photo-production experiments !

  34. Comments on statistical significance • Using to estimate statistical significance seems too optimistic. Even if we have firm knowledge on the background  CLb as LEP Higgs used is recommended. • When the background is estimated from the fit of sideband, the likelihood ratio with D.O.F. taken into consideration is a better estimator of statistical significance. • In this case, the uncertainty of all possible background shapes should be included in the uncertainty of significance. • Do not optimize/tune the cuts on the data!Determine the cuts based on MC optimization before looking at data. • The sys. uncertainty on significance from “bias” cut is hard to estimate. • “Look elsewhere” effect may reduce the significance by 1~2σ.

  35. X(3872)

  36. First observed by Belle Experiments in:

  37. M(p+p-J/y) –M(J/y) Belle y’ppJ/y at 90% C.L. X(3872) 10σeffect

  38. X(3872) at CDF and D0 5.2  effect 11.6  effect

  39. X(3872) at BaBar • The significance is low (about 3.5 σ), but its production rate is consistent with Belle: BaBar 3.5 σ effect

  40. Search for B X(3872) -K at BaBar • No evidence of X(3872) - is observed in B0X-K+, B-X-K0s withX(3872) - J/  - 0. • So, isovector hypothesis of X(3872) - disfavored.

  41. CLEO – γγFusion and ISR (90% C.L) Consistent with Yuan et al. estimation from BES data: JPC=1- - disfavoured

  42. New decay mode observed at Belle • Belle observed a new decay mode of X(3872)  *J/  +-0J/ • G(XwJ/y)/G(Xp+p- J/y) = 0.8 ±0.3± 0.1 Nevt=10.0 ± 3.6 Signif = 5.8s M(J/yp+p-p0) BK X(3872) M(p+p-p0)

  43. No other decay modes of X(3872) are observed • So far, it is only observed in J/and*J/ modes. 90% C.L. upper limits (most from Belle): • Non-observation of DD modes suggests that JP=0+, 1-, 2+,…, is ruled out. BaBar

  44. Is X(3872) a Charmonium? • All possible charmonium assignments seem to have difficulties (S.L. Olsen, hep-ex/0407033):

  45. DD* “Molecular State”? • MX(3872) is very close to MD + MD*. • It was suggested that a DD* multi-quark “molecular state” have large BR(XD0D00). Belle observes: Some theoretical calculations predict the above ratio is small.(Swanson’s talk in Session 10) • Swanson also predicts: Consistent with Belle new observation. at 90% C.L.

  46. DsJ(2632)

  47. DsJ(2317) andDsJ(2460) BaBar - DsJ(2317) CLEO Belle DSJ(2317) DSJ(2317) DSJ(2460) DSJ(2460) DSJ(2460)

  48. DSJ(2632) at SELEX • A narrow resonance was observed in mode. • Nevent = 45.0  9.3 • The significance is about 7.2 σ using . Probability of 6 bins region with > 100 events anywhere on this plot with background of 54.4+/-2.5: 3x10-6 ~4.6σ DsJ(2632) (Talk given by P.S. Cooper at PIC 2004)

  49. DSJ(2632) was also observed in D0K+ mode. • Nevent = 14.0  4.5 • The significance is about 5.3 σ (?) using .

  50. Properties ofDSJ(2632) • Mass: 2632.6  1.6 MeV( above D(*) K threshold ) • Narrow Width: < 17 MeV at 90% C.L. • Unusual decay pattern: What is it? • First radial excitation of DS*(2112)? • A csg hybrid? • A tetraquark or molecular state? ( Y.Q. Chen and X.Q. Li, hep-ph/0407062;K.T. Chao, hep-ph/0407091; T. Barnes et al., hep-ph/0407120; Y.R. Liu et al., hep-ph/0407157 … )  Next talk

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