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Recent J/  Results from BESII

Recent J/  Results from BESII. Nengfeng ZHOU Representing BES Collaboration Institute of High Energy Physics, CAS Rencontres de Moriond 2005 QCD AND HIGH ENERGY HADRONIC INTERACTIONS. Outline. Introduction Multiquark candidates at BES * pp threshold enhancement in

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Recent J/  Results from BESII

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  1. Recent J/ Results from BESII Nengfeng ZHOU Representing BES Collaboration Institute of High Energy Physics, CAS Rencontres de Moriond 2005 QCD AND HIGH ENERGY HADRONIC INTERACTIONS

  2. Outline • Introduction • Multiquark candidates at BES *pp threshold enhancement in * p threshold enhancement in * Kthreshold enhancement in • Study of the light scalar mesons • Study of the excited baryon states • Measurements of some J/ decays • Summary

  3. Introduction World J/ and (2S) Samples (×106) BESII Detector BESII 58MJ/ J/ BESII 14M(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 (2S)

  4. Multi-quark candidates • 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）

  5. 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 Phys. Rev. Lett., 91 (2003) 022001

  6. Observation of an anomalous enhancement near the threshold of mass spectrum at BES II  Data/MC The clear Λ signal in data shows high purity of signal.

  7. Phase Space PRL 93 (2004) 112002 Data Data

  8. Near threshold enhancement is also observed in Fix the parameters, 4 away from phase space.

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

  10. PWA is performed for enhancement • possible N* and *states listed in PDG are fitted • N(1720), N(1900), (1520), (1690), … • manydifferent combinations are tried • different form factors are used • different JP of Nx is tried

  11. An abnormal enhancement is observed in the mass threshold of MK • Its mass and width: (large uncertainty near threshold, high statistics is crucial!) Mass 1500~1650MeV Width70~110MeV JP favors 1/2- • large BR(J/pNx)Br(NxK) (2*10-4). What is it?? Possibly N*(1535) with large coupling to K Kmolecular state ??

  12. Light Scalar Mesons:σ, κ, f0(980), f0(1370), f0(1500), f0(1710), f0(1790)

  13. Why are light scalar mesons interesting? • There have been hot debates on the existence of  and. • Lattice QCD predicts the 0++ scalar glueball mass from 1.5 - 1.7 GeV. f0(1500) and f0(1710) are good candidates.

  14. The  pole in   M(+-) Pole position: MeV PLB598, 149 (2004)

  15. at BES BES II Preliminary • BES II observed in J/K*  KK. • Preliminary PWA results Pole position:

  16. Study of f0(980), f0(1370), f0(1500), f0(1710) from:

  17. f0(980) at BES • Important parameters from PWA fit: • Large coupling with KK indicates big component in f0(980) f0(980) f0(980)

  18. f0(1370) at BES • There has been some 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

  19. f0(1710) at BES • Clear f0(1710) peak in J/  KK. • Nof0(1710) observed in J/   ! f0(1710) NO f0(1710)

  20. f0(1710) in J/  KK PWA analysis shows one scalar. Phys. Rev. D 68 (2003) 052003

  21. f0(1710) 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)? BES II Preliminary

  22. f0(1500) at BES • One scalar with a mass = 1466  6  16 MeV is needed in J/ , is it f0(1500)? Why the mass is different from PDG? • No peak directly seen in , KK, , KK.

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

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

  25. Excited baryon states The evidence of 2 new N* peaks N*(1520) N*(1535) N*(1650) N*(1675) N*(1680) N*(1440)? ? Missing mass spectrum (GeV/c2)

  26. Fitting formula : momentum of : proton momentum in Mx frame ► Possible new N* resonance ►Detailed information needs PWA Submitted to P. R. L., hep-ex/0405030

  27. Measurements of J/ decays

  28. Measurement of J/ → +-0 from direct J/ decay: from (2S) decay: ******************* Br(J/ →+-0) = (21.350.041.85)10-3 Br(J/ →+-0) = (20.90.21.1)10-3 Combined BES value: (21.01.1)10-3 PDG: (15.0  2.0)  10-3 inconsistent ! Phys. Rev. D 70, 012005 (2004)

  29. First measurement of J/  f2(1270)f2(1270)4 2nd polynomial backgrounds J/f2 f2  f2 background The invariant mass spectrum of  + - with mass cut |M + - - 1.27|<0.185GeV for another  + - pair is used to fit the signal. Four components are used in the fit. The branching ratio is measured for the first time to be: PRD70, 112008 (2004).

  30. First measurement of J/2( + - ), 3( + - )   Clear  signal can be seenin the distribution of M from J/ 2( + - ). Clear  signal can be seenin the distribution of M from J/ 3( + - ). The branching ratios of J/2( + - ), 3( + - ) are measured for the first time: Br (J/ 2( + - )) = (2.26±0.08±0.27)×10-3 Br (J/ 3( + - )) = (7.24±0.96±1.11)×10-4

  31. Summary • An threshold enhancement is observed in decay. • The p and K threshold enhancements are observed in decay. • Study of the scalars: , , f0(980) ,f0(1370), f0(1500), f0(1710) • New N* peaks in • Measurements of J/ decays are performed, some of the channels are first observation.

  32. Thank you!

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