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R Group Working Report

R Group Working Report. Haiming Hu Representing R Group. BES Annual Shanxi, May. 23-26, 2004. Outline R&QCD data taking e + e - →proton-antiproton cross section e + e - →  +  -  +  - form factor The fit of the excited ψ -family resonant parameters Conclusions / Perspectives.

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R Group Working Report

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  1. R Group Working Report Haiming Hu Representing R Group BES Annual Shanxi, May. 23-26, 2004 • Outline • R&QCD data taking • e+ e- →proton-antiproton cross section • e+ e- →+-+- form factor • The fit of the excited ψ-family resonant parameters • Conclusions/Perspectives

  2. R and QCD R98 and R99 results Comments on the Rexp and RQCD ☻Deviate about 1σ in wide region 2.2-2.7GeV. Systematic Error?Hitting the new physics? ☺Central values of Rexp and RQCDcoincide at 2.0, 2.8-3.2GeV. Due to error? True agreement ?

  3. R&QCD Data Taking Jan.3 – Feb. 7 2004 Analysis by the programs of R99 measurement Data quality check Jin Yi’s report In general, the R&QCD data quality is good.

  4. The cross section of e+ e- +-+- ① 2 Yuan Jianming Tong Guoliang Hu Haiming The measurement of hadronic form factor may promote the understand to strong interaction, which give the expression to electro-magnetic vertex with influence of the strong interaction.Forthe processe+ e-+-+- The cross section and the Form factor measured by CDM,ND, DM2, OLYA groups between 1-2 GeV

  5. The cross section of e+ e- +-+- ② Back-ground analysis Event selection Cross section

  6. The cross section of e+ e- +-+- ③ Two analysis have been done with reconstructed R scan data by V101 and then V103 respectively, the number of events from V103 is consist with V101 except at energy points 2.9 and 3.0 GeV. The efficiencies estimated by SIMBES are lower about 40% than by BOSER, The cross section are about 1.6 to 2.0 times as large as former. The cross sections and the form factors measured using SOBER/SIMBES seems consistent/not consistent with the low energy experiments by other groups. But more check and analysis have to do.

  7. The cross section of e+ e- +-+- ④ BES V103& SIMBES Cross section BES V101& SOBER Cross section Can not fit the theory by V103 and SIMBES results together with the low energy experiments, they are not consistent with each other obviously. Form factor

  8. The EM form factor of proton Li Huihong

  9. The Conserved Vector Current – SU(2) W: I=1 &V,A CVC: I=1 &V : I=0,1 &V  e+   hadrons W e– hadrons fundamental ingredient relating long distance (resonances) to short distance description (QCD) Hadronic physics factorizes in Spectral Functions: Isospin symmetry (CVC) connects I=1 e+e– cross section to vectorspectral functions: branching Fractionsmass spectrum kinematic factor (PS)

  10. The fit of the excited ψ-family resonant parameters ① Hu Haiming Huang Guangshun • The 4 excited -family resonant Structure was scanned in 1999.

  11. The fit of the excited ψ-family resonant parameters ② • The resonant parameters were fitted in 2002, the preliminary results were reported at BES Anuual02. The memo about the parameter fit has submitted to BES Collaboration, and some reviews came . The preliminary results at BES02 The fit result by K.K.Scth hep-ex/0405007 A simple BG and constant width was assumed. The two experiments by CB and BES are in good agreement

  12. The fit of the excited ψ-family resonant parameters ③ Fit R values iteratively, the polynomial and QCD BG forms were used Fit the observed cross section, the DASP type BG form was used

  13. The fit of the excited ψ-family resonant parameters ④ Main review from the BES referees • The problem about the reliable QED backgrounds form used • DASP typepolynomial formQCD-like form The problem about the correct energy-dependent hadronic width for the wide resonance. AT BES02 report, a form of the total width derived from potential model of quantum mechanics was used Eichten model predicts the decay channels:

  14. The fit of the excited ψ-family resonant parameters ⑤ Some attempts to meet referee’s requests The continuum backgrounds form based on QCD and Lund area law The lowest cross section for the exclusive channel The QED cross section for quark pair production The string fragmentation probability in Lund area law

  15. The fit of the excited ψ-family resonant parameters ⑥ Some attempts to meet referee’s requests Energy-dependent hadronic width The effective interaction theory was used Interaction matrix element: The decay types concerned: The interactive Hamiton: Hadronic decay width:

  16. The fit of the excited ψ-family resonant parameters ⑦ Some attempts to meet referee’s requests The running mass parameter means the principal value of integral

  17. The fit of the excited ψ-family resonant parameters ⑧ Some attempts to meet referee’s requests The comparison between experiment and theory/model The parameters were putted by hand, i.e. not fit yet R value by experiment R value by theory & model Total continuum GB Continuum QCD BG with u,d,s qurks: RQCD(u,d,s) Continuum two-body BG from e+e-→DD’ Continuum three-body BG from e+e-→DMD’

  18. e+e–Radiative Corrections Multiple radiative corrections are applied on measured e+e– cross sections • Situation often unclear: whether or not - and if - which corrections were applied • Vacuum polarization (VP) in the photon propagator: • leptonic VP in general corrected for • hadronic VP correction not applied, but for CMD-2 (in principle: iterative proc.) • Initial state radiation (ISR) • corrected by experiments • Final state radiation (FSR) [we need e+e–  hadrons () in disper-sion integral] • usually, experiments obtain bare cross section so that FSR has to be added “by hand”; done for CMD-2, (supposedly) not done for others

  19. 2002 Analysis of ahad • Motivation for new work: • New high precision e+e– results (0.6% sys. error) around  from CMD-2 (Novosibirsk) • New results from ALEPH using full LEP1 statistics • New R results from BES between 2 and 5 GeV • New theoretical analysis of SU(2) breaking CMD-2PL B527, 161 (2002) ALEPH CONF 2002-19 BES PRL 84 594 (2000); PRL 88, 101802 (2002) Cirigliano-Ecker-Neufeld JHEP 0208 (2002) 002 • Outline of the 2002 analysis: • Include all new Novisibirsk (CMD-2, SND) and ALEPH data • Apply (revisited) SU(2)-breaking corrections to data • Identify application/non-application of radiative corrections • Recompute all exclusive, inclusive and QCD contributions to dispersion integral; revisit threshold contribution and resonances • Results, comparisons, discussions... Davier-Eidelman-Höcker-Zhang Eur.Phys.J. C27 (2003) 497

  20. The Problem Relative difference between  and e+e– data zoom

  21. The Changes in the Input Data • ee data bugs found by CMD-2 Coll. in their analysis • 2.2-2.7% luminosity correction from change in Bhabha • 1.2-1.4% change in  • both changes affect event separation ee /  /  0.6% systematic error unchanged  and  contributions re-evaluated (new SND, corrected CMD-2) •  data no change,precision improved slightly with new L3 result on B0

  22. The New Situation Relative difference between  and e+e– data zoom

  23. –0: Comparing ALEPH, CLEO, OPAL Shape comparison only. Both norma-lized to WA bran-ching fraction (dominated by ALEPH). • Good agreement observed between ALEPH and CLEO • ALEPH more precise at low s • CLEO better at high s

  24. Testing CVC Infer branching fractions from e+e– data: Difference: BR[ ]– BR[e+e– (CVC)]: leaving out CMD-2 : B0 = (23.69  0.68) %  (7.4  2.9) % relative discrepancy!

  25. Results: theData &the Theory use data • Agreement bet-ween Data (BES) and pQCD • Better agree-ment between ex-clusive and inclu-sive (2) data than in 1997-98 analyses use QCD

  26. Results: the Compilation Contributions to ahadfrom the different energy domains:

  27. Discussion • The problem of the  + – contribution : • Experimental situation: • corrected CMD-2 results in agreement with  data up to s  0.7 GeV2 within  2 % per point: large improvement! • older e+e exp. low in this range by  4 % (OLYA), almost within systematics • CMD-2 and older e+e exp. low /  in the range 0.7- 0.9 GeV2 by  9 % • ALEPH and CLEO  spectral functions in good agreement within errors, OPAL deviates more (especially below 0.4 GeV2) • Concerning the remaining line shape discrepancy (0.7- 0.9 GeV2): • e+eis consistent among experiments, large radiative corrections applied, preliminary results from KLOE in agreement •  is consistent among experiments in different environments • SU(2) corrections: basic contributions identified and stable since long; overall correction applied to  is (– 2.2 ± 0.5)%, dominated by uncontroversial short distance piece; additional long-distance corrections found to be small At present, we believe that it is still unappropriate to combine and e+e– : [ –e+e ] = (–14.7 ± 6.9exp ± 2.7rad ± 2.8SU(2)) 10–10 1.9 

  28. Final Results (exp and theo errors added in quadrature) [DH’98] [DEHZ’03] Hadronic contribution from higher order : ahad [(s/)3] = – (10.0 ± 0.6) 10–10 Hadronic contribution from LBL scattering : ahad [LBL] = + ( 8.6 ± 3.5) 10–10 inclu-ding: Observed Difference with Experiment:

  29. Conclusions/Perspectives • Hadronic vacuum polarization creates dominant systematics for SM predictions of the muon g-2 • 2002 analysis of leading hadronic contribution motivated by new, precise e+e–(0.6% systematic error) and  (0.5% error on normalization) data • Correction of  spectral function for SU(2) breaking on better ground • Radiative (VP and FSR) corrections in e+e–: major source of systematics • All exclusive and inclusive as well as resonance contributions re-evaluated • 2003 re-analysis using corrected CMD-2 results • We still conclude with two incompatible numbers from e+e–and  , leading to SM predictions that differ by 1.9  [e+e–]and 0.7  [ ] from experiment • The key problem is the quality of the experimental data... • Future experimental input expected from: • More CMD-2 results to come, new VEPP, CLEO & BES as  /charm factories • B factories: will improve the line shape from , but not the normalization • ISRproductione+e–  hadrons + @ KLOE, BABAR

  30. BaBar ISR : e+e-   • Boost: • acceptance down to threshold • easier particle ID • Ratio cancels: • luminosity • ISR and VP radiative corrections • many efficiencies (photon, tracking) • Small corrections: • trigger efficiency (track and EMC triggers) • FSR corrections, can be studied exp. Major work: particle ID efficiency matrix (P,,)

  31. BaBar ISR : e+e-  22 preliminary BaBar 89.4fb-1 • very clean sample (background~2% ) • whole mass range is covered • large statistics (~75k events), syst. error ~5%

  32. BaBar ISR : impact on g-2 • most important  channel still under study (need <1% syst) • BaBar is the only experiment covering at the moment the energy range 1.4 - 2 GeV where previous results are not accurate • illustrate power of BaBar data with available 4 results: • contribution to ahad (1010) from 2+ 2 (0.56 – 1.8 GeV) • from all e+ e exp. 14.21  0.87exp  0.23rad • from  data 12.35  0.96exp  0.40SU(2) • fromBaBar 12.95  0.64exp  0.13rad

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