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New Results and Prospects of Light Hadron Spectroscopy

New Results and Prospects of Light Hadron Spectroscopy

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New Results and Prospects of Light Hadron Spectroscopy

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  1. New Results and Prospectsof Light Hadron Spectroscopy Shan JIN Institute of High Energy Physics (IHEP) jins@mail.ihep.ac.cn Presented by Yi-Fang Wang Charm 2007 Ithaca, August 7, 2007

  2. Outline • New results on 0-+ mesons • New results on 0++ mesons • New results on 1-- mesons • New results on baryons at BESII • Prospects of glueball searches at BESIII

  3. New results on 0-+ mesons

  4. (1760) in at BESII

  5. Phys. Rev. D 73 (2006) 112007   M(+-0)(GeV/c2) M(+-0)(GeV/c2) M(+-0)(GeV/c2) M(+-0)(GeV/c2)  sideband  signal with multiple entries  signal after best candidate selection (best w masses)

  6. M() M() Side-band Phase Space Eff. curve

  7. PWA analysis f0(1710) f0(1790) f0(1810) Total (1760) > 10  f0 (1760) f0(1710) Using observed mass and width for f0(1810) in J/  f2(1640) f2(1910) f2(160) f2(1910) BG BG M() M() (GeV/c2)

  8. The existence of (1760) is confirmed • Its mass and width were first correctly measured with PWA. Phys. Rev. D 73 (2006) 112007

  9. Candidate of 0-+ baryonium

  10. Phys. Rev. Lett. 95, 262001 (2005) Observation of X(1835) in at BESII Statistical Significance 7.7  The +- mass spectrum for  decaying into +- and  

  11. Phys. Rev. Lett. 91, 022001 (2003) Observation of an anomalous enhancement near the threshold of mass spectrum at BES II J/ygpp BES II acceptance weighted BW +3 +5 -10 -25 M=1859 MeV/c2 G < 30 MeV/c2 (90% CL) c2/dof=56/56 0 0.1 0.2 0.3 M(pp)-2mp (GeV) 3-body phase space acceptance

  12. Re-fit to J/p pbar including FSI Include FSI curve from A.Sirbirtsev et al. ( Phys.Rev.D71:054010, 2005) in the fit (I=0) M = 1830.6  6.7 MeV  < 153 MeV @90%C.L. In good agreement with X(1835)

  13. Candidate of 0-+ ppbar Bound State • X(1835) could be the same structure as ppbar mass threshold enhancement X(1860)/X(1830). • It could be a ppbar bound state since it dominantly decays to ppbar when its mass is above ppbar mass threshold. • Its spin-parity should be 0-+: this would be an important test. There is already an (1760) nearby , so that  X(1835) is very likely to be an unconventional 0-+ meson.

  14. This strong threshold enhancement is NOT observed in at CLEO • This result cannot be explained by pure FSI effect, since FSI is a universal effect. FSI interpretation of the narrow and strong ppbar threshold enhancement is disfavored. • This indicates that X(1860) has a production property similar to ’ meson. c.f.: Phys.Rev.D73, 032001(2006) No enhancement near threshold

  15. No strong threshold enhancement is observed in at BESII • FSI interpretation of the narrow and strong ppbar threshold enhancement is disfavored. • This again indicates that X(1860) has a production property similar to ’ meson. c.f.: Phys.Rev.Lett.99, 011802 (2007) No significant narrow strong enhancement near threshold (2.0  if fitted with X(1860))

  16. This strong threshold enhancement is NOT observed in at BESII • This again disfavors FSI and indicates that X(1860) has a production property similar to ’ meson. c.f.: • This also indicates X(1860) may have strong coupling to gluons as ’ meson. BESII Preliminary No narrow strong enhancement near threshold

  17. Summary of new studies on ppbar mass threshold structure X(1860) • Pure FSI effect cannot explain X(1860) structure. • X(1860) has production properties similar to ’ meson  • Why a baryonium (candidate) has a production properties similar to ’ meson? • ’ excitation? Why an ’ excitation dominantly decays into ppbar above ppbar mass threshold?

  18. New results on 0++ mesons

  19. Observation of  mass threshold enhancement at BESII Phys. Rev. Lett. 96,162002 (2006)

  20.   recoiling against  J/    +  +    +-0 K+ K- • We studied DOZI process:

  21. Side-bands A clear mass threshold enhancement is observed Acceptance

  22. The radiative decay of J/ has been observed in the 58M J/ data. • A significant structure of  has been found near the mass threshold. • PWA shows the structure favors 0++, with a mass , width 1052028 MeV, and the corresponding branch ration is (2.610.270.65)x10-4. • It could be a multiquark/hybrid/glueball state. • Its relation with f0(1710),f0(1790)?

  23. PWA of J/  +- and 00 at BESII Phys. Lett. B 642 (2006) 441

  24. PWA of J/  +- and 00 The channels fitted in PWA: M(+- ) M(00 )

  25. PWA components: all 2++ all 0++

  26. PWA results • Lower 0++ : 0++ is strongly preferred over 2++ • f0(1370) cannot be excluded. • Higher 0++: f0(1710) or f0(1790)

  27. Phys. Lett. B 642 (2006) 441

  28. About f0(1500) • It is first clearly observed in J/psi radiative decays. • Its production rate in J/psi radiative decays: • The production rate of f0(1500) in J/psi radiative decays is lower than f0(1710): • It indicates f0(1710) has stronger coupling to gluons than f0(1500) which one contains more glueball content?

  29. New results on 1-- mesons

  30. New observation of a broad 1-- resonance in J/  K+K- 0 at BESII Phys. Rev. Lett. 97 (2006) 142002

  31. K*(1410) 0 X(1580) K*(892) 0 sideband background ? J/ K+K-0 PID and kinematic fit can significantly reduce the dominant background from J/  + - 0.

  32. Partial Wave Analysis of J/  K+K- 0 events • Four decay modes are included : • Amplitudes are defined by Covariant tensor formalism B.S. Zhou and D.V. Bugg, Eur. Phys. J. A16, 537(2003) • BW with energy-dependent width J.H. Kuhn, A. Satamaria, Z. Phys. C48, 445 (1990).

  33. Partial Wave Analysis of J/  K+K- 0 events • Parity conservations in J/  K+K- 0requires that spin-parity of K+K- should be 1--,3--,… • PWA fit with and phase space (PS) gives: ( can be ruled out by much worse likelihood ) • X pole position • big destructive interference among and PS

  34. Broad X cannot be fit with known mesons or their interference • It is unlikely to be (1450), because: • The parameters of the X is incompatible with (1450). • (1450) has very small fraction to KK. From PDG: • It cannot be fit with the interference of (770) , (1900) and (2150): • The log-likelihood value worsens by 85 (2=170).

  35. How to understand broad X(1580)? • Search of a similar structure in J/  KSK will help to determine its isospin. • X(1580) could have different nature from conventional mesons: • There are already many 1- - mesons nearby. • Width is much broader than other mesons. • Broad width is expected for a multiquark state.

  36. A structure at 2175MeV was observed in e+e-f0(980), via initial-state radiation at BABAR. Evidence of a new 1-- resonance Y(2175) at BaBar Phys. Rev. D 74 (2006) 091103(R)

  37. What is Y(2175)? • A conventional state? • An analog of Y(4260) ( )? • An 4-quark state? • More experimental information needed, especially we can search for it in J/psi decays at BESII and BESIII.

  38. New results on baryons at BESII

  39. N* in . at BESII 0 BES II Preliminary  M2(p0) M

  40. BES II Preliminary N* in . Resonances used in the PWA The best results to now

  41. N* in . BES II Preliminary  data  Fit results Fit results agree with data reasonably, especially in the low mass region. The comparison between data and PWA fit results.

  42. N* in . BES II Preliminary

  43. K mass threshold enhancement

  44. Observation of a strong enhancement near the threshold of mass spectrum at BES II NX* BES II PS, eff. corrected (Arbitrary normalization)

  45. A strong enhancement is observed near the mass threshold of MKat BES II. • Preliminary PWA with various combinations of possible N* and Λ* in the fits —— The structure Nx*has: Mass 1500~1650MeV Width70~110MeV JP favors 1/2- The most important is: It has large BR(J/ψ  pNX*) BR(NX* KΛ)2 X 10-4 , suggesting NX* has strong coupling to KΛ.

  46. Nx* is N(1535)? • From: If Nx* is N(1535), we would have Then N(1535) would have very large ssbar component (a 5-quark system).

  47. Such a big coupling to K of N(1535) is NOTobserved in process at SAPHIR Phase Space shape

  48. A ΛK resonance predicted by chiral SU(3) quark model • Based on a coupled-channel study of ΛK andΣK states in the chiral SU(3) quark model, the phase shift shows the existence of a ΛK resonance between ΛK andΣK mass threshold. ( F. Huang, Z.Y. Zhang et al. Phys. Rev. C71: 064001, 2005 ) Ecm – ( MΛ+MK ) (MeV)

  49. The KΛ mass threshold enhancement NX(1610) could be a KΛ bound/resonant state. • Whether NX(1610) is N(1535) needs further study.

  50. Study of at BESII • No obvious N* in Dalitz plot. • We measured: BES II Preliminary