1 / 32

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

aliya
Download Presentation

Recent J/  Results from BESII

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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!

More Related