1 / 39

Recent Results from BES J/ and  (3770) Decays

Recent Results from BES J/ and  (3770) Decays. Xiaoyan SHEN Representing BES Collaboration Institute of High Energy Physics (IHEP) CAS, Beijing, P.R.China shenxy@ihep.ac.cn 2nd International Workshop on Heavy Quarkonium Sept. 20 – 22, 2003, Fermilab. Outline. Introduction

vinaya
Download Presentation

Recent Results from BES J/ and  (3770) Decays

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 Results from BES J/ and  (3770) Decays Xiaoyan SHEN Representing BES Collaboration Institute of High Energy Physics (IHEP) CAS, Beijing, P.R.China shenxy@ihep.ac.cn 2nd International Workshop on Heavy Quarkonium Sept. 20 – 22, 2003, Fermilab

  2. Outline • Introduction • Study of  and  • Precise measurement of • Study of • Measurement of • Study of the excited baryon states -- N* in the decay of -- N* and * in the decay of • (3770)  J/ . • Summary

  3. J/ data samples CBAL 2.2M J/ events DM2 8.6M J/ events BESII 58MJ/ events MKIII 5.6M J/ events BESI 7.8M J/ events MKII 5.6M J/ events

  4. Introduction to J/ Physics 3-gluon Electromagnetic Radiative Via c • a good lab for studying hadron spectroscopy • a good lab for excited baryon states • hunting for glueballs in J/ radiative decays

  5.  in J/ -- 4 good charged tracks with total Q=0 -- 2 or more good photons -- Particle ID by TOF and dE/dx -- 24C (J/++) < 40 -- Selection of 0 : | M  - M 0 | < 40 MeV -- Selection of  : | M +0- M | < 40 MeV

  6. BESII 58M J/ BES II Preliminary

  7. Two methods are used: Method 1Method 2 M+ <1.55GeV whole M+ region treats  as a particle uses the  decay info. J/f2(1270) J/f2(1270)   f0(980) f0(980) b1(1235) b1(1235) 0 ’(1450) phase space f2(1565) f2(2240)

  8. Pole position of  (BESII preliminary) If the σ amplitude is written as: pole: (542 ±10 ± 40 ) – i(249 ±25 ±60) MeV If (s) = 0(s)/ (M2) pole: (516 ± 15 ± 50 ) – i(313 ±25 ±65) MeV If  = constant pole: (540 ± 10 ± 40 ) – i(267 ±30 ±65) MeV

  9. Fit to the J/→+ b1(1235) BES II Preliminary preliminary f0 contribution f2 contribution

  10.  in J/ K*K and K+K- • 4 good charged tracks with total Q=0 • Particle ID by TOF and dE/dx, prob(K/ ) > 0 • 24C (J/K+K +) <40 • prob4C(K+K + )probpid(K+)  probpid(K)  probpid(+)  probpid() > other particle assump. ( ++ ;K+KK+K; K + ) • Remove KS,  by • | M+ - MKS| > 0.04 GeV; | MK+K - M | > 0.02 GeV

  11. Before K*(892) 0 cut BES II Preliminary After K*(892) 0 cut

  12. Method 1: selecte K*0(892): | M+ K - 0.892| < 0.08GeV study K+ spectrum BES II Preliminary If  is treated as a resonance,  contribution Pole position: MeV

  13. Method 2 Fit J/→K+K-+- whole phase space BES II Preliminary If amplitude is written as: K0(1430) is fitted with a flatte formula: MeV Pole position:

  14. Precise measurement of J/ The angular distribution of two baryon final states can be written as Where is the angle between the baryon direction and the positron beam direction Theoretical models from first order QCD give various  value predictions.

  15. Status ofJ/ theo1:S.L.Brodsky,G.P.Lepage, Phys. Rev. D24, 2848(1981) theo2:M.Claudson,S.L.Glashow,M.B.Wise, Phys. Rev. D25, 1345(1982) theo3:C. Carimalo, Int. J. Mod. Phys. A2, 249(1987)

  16. BES measurement on J/ =0.676±0.036±0.027 , agrees with theo3 sys. error Br=(2.26 ±0.01 ±0.12) ×10-3 BES II Preliminary sys. error

  17. Study of J/V (V=,) • Theoretical prediction for (1440) • state  : =9 : 2 • Pure glueball:  : =1 : 1 • MARKIII Results • (1440) →   Mass= 1432 ± 8MeV = 90 ± 26 MeV B(J/ →  ) ×B( →  ) =(0.64±0.12±0.07)×10-4 • (1440) →   B(J/ →  ) ×B( →   ) < 1.6×10-4 (90% C.L.)

  18. BES results on (preliminary) ’ f1(1285) (1440) BES II Preliminary BCK from J/→0,

  19. BES results on (preliminary) BES II Preliminary 48.4847.14 events B(J/X)=(0.310.30)10-4 B(J/X)<0.8210-4 95% C.L. After BCK subtraction

  20. Measurement of J/→ +-0 (preliminary) • Absolute Measurement from BESII 58M J/ Decays • Further Criteria(continued): such as J/→’ • The deposited energy of two charged pions in Barrel Shower Counter less than 2GeVto reject J/→()e+e- • Remaining BG less than 1% relative from MC study (BG mainly comes from J/  K+K- 0 and ’). • Signal selection efficiency is 17.83% • Basic Criteria: • Two oppositely good charged tracks • At least two good photons • 5C kinematic fit 2(+-0)15 • Further Criteria: • 5C kinematic fit 2(+-0)2(K+K-0) toreject J/→ K+K-0 • (+-)10to reject  conversion • The photon angle in the 0 rest frame |cos|<0.98to reject radiative events,

  21. BES II Preliminary m+0 00 m+- +- m-0 -+ +0 B(J/ →+-0) =(21.350.041.85)10-3 Systematic errors include: BG from continuous energy region(1%), reconstruction of each charged track(2%), photon detection(2%), 5C kinematic fit(2.9%), further criteria (1%), MC model uncertainty(3%), BG uncertainty(1%) and J/ total number(5%) TOTAL  8.7%

  22. Relative Measurement from 14M (2S) Decays BES II Preliminary Similar cuts are used for process I and II , many systematic errors can be cancelled. BESII 14M (2S) : B(J/→+- 0) =(20.90.21.1)10-3 (preliminary) PDG: (15.0  2.0)  10-3 inconsistent !

  23. Discussion on BESII J/→+- 0 results BESII 58M J/ : B(J/ →+- 0)=(21.350.041.85)10-3 is well consistent with BESII 14M (2S) :B(J/→+- 0)=(20.90.21.1)10-3 • Combining BESII J/ , (2S) : B(J/→+- 0)=(21.01.1)10-3 • Inconsistent with PDG : J/→ +-0 = (152)10-3 • Extensive and careful checks on BESII SIMBES DATA consistencies have been made, such as MDC reconstruction, kinematic fit χ2 , photon detection, Barrel Shower Counter performance. No significant BESII SIMBES DATA inconsistency has been found

  24. J/ ----- : DATA : SIMBES An example of BESII SIMBES DATA consistency check: 5C kinematic fit 2(+- 0)<15 efficiency systematic error is about 2.9% 4C-fit 2(+- 0) J/ ----- : DATA : SIMBES Cut here 5C-fit 2(+- 0)

  25. Study of Excited Baryon States • Probe the internal structure of light quark baryons • Search for missing baryonspredicted by quark model • Obtain a better understanding of the strong interaction force in the non-perturbative regime • Jefferson Lab. electro&photo-production exps. • CB-ELSA facility at Bonn University • SPRING8 in Japan • GRAAL at Grenoble of France started exps

  26. J/ decays • relatively large branching ratios (PDG2002) (58M J/)

  27. Pure isospin 1/2 Feynman diagram of the production of For and , N and N systems are limited to be pure isospin 1/2.

  28. from BESII data • Events selection • 2 good charged tracks • Q1+Q2 = 0 • |cos| < 0.8 • PID: TOF and dE/dx • Mp > 1.15 GeV • 0.88<Mmiss<1.0 GeV BES II Preliminary

  29. N*(1520) N*(1535) N*(1650) N*(1675) N*(1680) N*(1440) ? BES II Preliminary N* in BG estimation • Estimate the BG from • the fitting of the data. • The Monte Carlo of • J/ inclusive decay • is also used in the • background analysis. • Background < 8%.

  30. N* in Sideband events • 1.1<Mmiss<1.15 • No bump around 2.0 GeV

  31. Fitting formulak : momentum of q : proton momentum in Mx frame BES II Preliminary ►Possible new N* resonance (preliminary) ►Detailed information needs PWA

  32. BES II Preliminary N* in BES II Preliminary

  33. N*(1650) BES II Preliminary from BESII data • Two clear peaks at 1520, 1690 MeV/c2 in pK mass • N* in K mass • PWA is being performed

  34. Search for the (3770) non- decay to +- J/ Motivation --- (3770) is believed to be a mixture of the 23S1 and 13D1states of the system and to decay almost entirely to pure . (P.A. Rapidis et al., (MARK-I), Phys. Rev. Lett. 39, 526(1978)) --- Recently, some theoretical calculation point out that(3770) could decay to non- final states. (H.J. Lipikin, Phys. Lett. B179, 278(1986), Y.P. Kuang, Phys. Rev. D65, 094024(2002) )

  35. Evidence of (3770)  J/ , J/  in a data set of 8.0 0.5 pb-1at BESII • 4 good charged tacks • PID based on TOF, dE/dx and BSC • COS > 20o Ell - ECM<2.5ll •  Mll - M<150MeV Pfit(2,4)>1% Rcoil mass of  Fitted mass of ll

  36. Background due to (2S) The number of background due to (2S) production around the nominal center-of-mass energy was estimated by Monte Carlo. Differential cross section for and productions at actual c.m. energy MC (400  data)

  37. Branching fraction (no K. F.) (8.83.3) - (1.9  0.2) events, (Kinematic Fit) (8.2  2.9) - (1.4  0.2) events

  38. Summary Based on BESII 58M J/ (preliminary) •  is clearly seen in J/. The pole position of  is determined. •  is studied in J/ K*K and K+K-. The pole position of  is determined. • Br.(J/ )= (2.26 ±0.01 ±0.12) ×10-3  = 0.676±0.036±0.027 • J/(1440), is observed, but no clear  signal

  39. Br(J/ →+- 0)=(21.01.1)10-3 • A possible “missing” N* is found in • PWA to BESII 58M data is in progress • In , two peaks around 1520 and 1690 MeV in pK massare clearly seen. • Evidence of (3770)  J/ .

More Related