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Recent BES II Results and Future Prospects

Recent BES II Results and Future Prospects. Zhipeng ZHENG Representing BES Collaboration Institute of High Energy Physics, CAS. Outline. Introduction New observations at BESII Study of the scalars BESIII/BEPCII project. Beijing Electron Positron Collider (BEPC).

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Recent BES II Results and Future Prospects

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  1. Recent BESIIResults and Future Prospects Zhipeng ZHENG Representing BES Collaboration Institute of High Energy Physics, CAS

  2. Outline • Introduction • New observations at BESII • Study of the scalars • BESIII/BEPCII project

  3. Beijing Electron Positron Collider (BEPC) L ~ 51030 /cm2s at J/ Ebeam~ 1 – 2.5 GeV BESI started running in 1989 BESII started running in 1997 BESIII will start running in 2008

  4. BESII Detector World J/ and (2S) Samples (×106) BESII 58MJ/ J/ BESII 14M(2S) (2S) • VC: xy = 100 m TOF: T = 180 ps • MDC: xy = 220 m BSC: E/E= 21 % • dE/dx= 8.5 %  = 7.9 mr • p/p=1.78(1+p2) z = 2.3 cm • counter: r= 3 cm B field: 0.4 T z = 5.5 cm

  5. BEPC / BES •  mass measurement • R measurement • New states in J/→g pp… • Candidates for Glueball • J/， ’，D and Ds physics… ￣ ￣

  6. World average (1991) Tau mass measurement,（1991－1992） BES result: Universality for lepton is stand up

  7. tau mass fit

  8. －  universality comparation from 1992 to 1996

  9. BEPC/BES R measurement

  10. New observations at BESII

  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) X(1860) c2/dof=56/56 0 0.1 0.2 0.3 3-body phase space M(pp)-2mp (GeV) acceptance

  12. X(1860) has large BR to pp • BES measured: • From Crystal Ball result, we estimate: • So we would have: Considering that decaying into pp is only from the tail of X(1860) and the phase space is very small, such a BR indicates X(1860) has large coupling to pp !

  13. B+ pp K+ at BaBar and Belle Belle BaBar 210 fb-1 BES II X(1860) • The pp threshold enhancement • observed in J/ decay is • different from the enhancements • observed by Belle and BaBar • in B decay. • The one in B decay can be • explained by fragmentation.

  14. This narrow threshold enhancement is NOT observed in (1S)pp at CLEO • This result cannot be explained by pure FSI effect, since FSI is a universal effect. FSI interpretation of the narrow and strong pp threshold enhancement is disfavored. PRD73, 032001(2006) No enhancement near threshold

  15. This narrow threshold enhancement is NOT observed in at BESII • This again disfavors FSI’ BESII Preliminary Observations of this structure in other decay modes are desirable. No narrow strong enhancement near threshold

  16. Search for the strong mass threshold enhancement X(1860) in • A strong mass threshold enhancement was observed in • No obvious strong mass threshold enhancement was observed in +3 +5 -10 -25 BESII preliminary M=1859 MeV/c2 G < 30 MeV/c2 (90% CL) acceptance Fit acceptance 0 0.1 0.2 0.3 X(1860) M(pp)-2mp (GeV)

  17. BES: X(1835) in Statistical Significance 7.7  7.7 X(1835) PRL 95 (2005) 262001

  18. Fit to J/ pp including FSI M = 1830.6  6.7 MeV  = 0  93 MeV Include FSI curve from A.Sirbirtsev et al.(hep-ph/ 0411386) in the fit (I=0) BES II Preliminary I=1 I=0 In good agreement with X(1835)

  19. X(1835) could be the same structure as pp mass threshold enhancement. • It is likely to be a pp bound state since it dominantly decays to pp when its mass is above pp mass threshold. • ’ mode is expected to be the favorable decay mode for a pp bound state below pp mass threshold G.J. Ding and M.L. Yan, hep-ph/0502127

  20. Observation of p mass threshold enhancement in J/pK-

  21. Observation of an anomalous enhancement near the threshold of mass spectrum at BES II Phys. Rev. Lett. 93, 112002 (2004) BES II 3-body phase space For a S-wave BW fit: M = 2075 12  5 MeV Γ = 90  35  9 MeV

  22. K- mass threshold enhancement

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

  24. A strong enhancement is observed near the mass threshold of MKat BES II. • Preliminary PWA with various combinations of possible N* 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.

  25. Observation of  thresholdenhancement in J/         DOZI OZI

  26. Clear  and  signals  M(K+K-)   M(K+K-) M(+-0) Dalitz plot   M2(g) M(+-0) M2(gw)

  27. A clear threshold enhancement is observed Phase Space Eff. curve Side-bands Side-bands do not have mass threshold enhancement!

  28. PWA shows: the enhancement favors 0++ over 0-+ and 2++ . • Is it the same 0++ observed in KK or  (f0(1710), or f0(1790)), or is it a glueball, or a hybrid …..? Further look in , K*K*,  …. is desirable ! Phys. Rev. Lett., 96 (2006) 162002

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

  30. 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.

  31. 1-- component What is the broad resonance? • JPC should be 1--, 3--, …(Parity conservation) • PWA results • Following components are neededK*(892), K*(1410), (1700), X • 1– is much better than 3— • Pole position of X is • Br • Big destructive interferenceamong X, (1700)and PS

  32. Study of the scalars • There have been hot debates on the existence of  and. • Lattice QCD predicts the 0++ scalar glueball mass in the range 1.5 - 1.7 GeV. f0(1500) and f0(1710) are good candidates.

  33. study  in study  in • studyf0(980), f0(1370), f0(1500), f0(1710)and f0(1790)in 0++

  34. The study of  • evidence for a low mass pole in the early DM2 and BESI data on J/   . • huge event concentration in the I=0 S-wave  channel seen in M~ 500 – 600 MeV in the pp central production exp. • to explain  scattering phase shift data， should be introduced in chiral perturbative theory. • FNAL E761 exp. D++-+ data

  35. The  pole in at BESII   M(+-) Different parameterizations of BW are used in PWA. Averaged pole: BES, PLB 598 (2004) 149

  36. observation of  in ’+-J/ • Measure the universal pole position (552 - i232 MeV) • World largest  signal (with ~ 40,000 tagged events) Phys. Lett. B 645 (2007) 19

  37. The study of  • A possible  pole is controversial. • Some analyses of LASS K scattering data need (800), some don’t. • Scadron et al. favors a nonet made up of , (800), f0(980) and a0(980). • Julich group used t-channel exchanges to explain K scattering data. • evidence of  in FNAL E791 data on D+ K-++ • slightly lower statistics of CLEO D0 K-+0 data find no evidence of  • FOCUS data on K+K-++ require K*0 interfere with either a constant amplitude or a broad 0+ resonance in K

  38. BES observed  in J/K*KKK A possible  pole is controversial. PWA result:  is needed in the fit. Pole position of : BES II 58 M J/ Phys. Lett. B 633 (2006) 681

  39. Study of other scalars • Lattice QCD: • the lightest scalar glueball in the region of 1.5- 1.7 GeV • Glueball searches should be performed in • simultaneously.

  40. 0++ states: f0(980),f0(1370), f0(1500), f0(1710), f0(1790) PDG 2006 values: f0(980): M = 980 10 MeV,  = 40 – 100 MeV  , KK f0(1370): M = 1200 – 1500 MeV,  = 200 – 500 MeV  2, 4, KK … f0(1500):M = 1507  5 MeV,  = 109  7 MeV  2, 4, , ’, KK … f0(1710):M = 1714  5 MeV,  = 140  10 MeV  2, 2K, 4, , ’ …

  41. f0(980) • Important parameters from PWA fit: • Large coupling with KK indicates big component in f0(980) f0(980) f0(980) Phys. Lett. B 607 (2005) 243

  42. f0(1370) • There has been debate whether f0(1370) exists or not. • f0(1370)clearly seen in J/  , but not seen in J/  . f0(1370) NO f0(1370) PWA 0++ components Phys. Lett. B 607 (2005) 243

  43. f0(1710) • Clear f0(1710) peak in J/  KK. • Nof0(1710) observed in J/   ! f0(1710) NO f0(1710) Phys. Lett. B 603 (2004) 138

  44. PWA analysis shows one scalar in 1.7 GeV region Phys. Rev. D 68 (2003) 052003

  45. New f0(1790)?? • A clear peak around 1790 MeV is observed in J/  . • No evident peak in J/  KK. If f0(1790) were the same as f0(1710), we would have: Inconsistent with what we observed in J/   , KK f0(1790) ?  f0(1790) is a new scalar ??

  46. Scalars in J/   Two scalars in J/  : • One is around 1470 MeV, may be f0(1500). • The other is around 1765 MeV, is it f0(1790) or f0(1710) or a mixture of f0(1710) and f0(1790)? Phys. Lett. B 642 (2006) 441

  47. OZI rule and flavor tagging in J/ hadronic decays • In J/ hadronic decays, an  or  signal determinesthe or component, respectively. OZI rule

  48. Unusual properties of f0(1370), f0(1710) and f0(1790) • f0(1710): • It dominantly decays to KK (not to )  • It is mainly produced together with  (not )  • What is it ? • f0(1370) and f0(1790) • They dominantly decays to  (not to KK)  • It is mainly produced together with  (not )  • What are they ? Scalar Puzzle

  49. Future Prospects BESIII/BEPCII project. Government approved. Started construction from the end of 2003.

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