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Measurement of spectral function in the decay

Motivation ~ Muon Anomalous Magnetic Moment ~ Event selection mass spectrum (unfolding) Evaluation of result. Yukiko Hirano (Nara Women’s Uni. , High Energy Physics Lab.) For the Belle collaboration.

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Measurement of spectral function in the decay

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  1. Motivation ~ Muon Anomalous Magnetic Moment ~ Event selection mass spectrum (unfolding) Evaluation of result Yukiko Hirano (Nara Women’s Uni. , High Energy Physics Lab.) For the Belle collaboration Measurement of spectral function in the decay Outline JPS 2003 in Sendai

  2. The prediction of Standard Model Muon Anomalous Magnetic Moment： hadron hadron Motivation~ Muon Anomalous Magnetic Moment ( ) ~ largest error from Hadron vacuum polarization JPS 2003 in Sendai

  3. Semi-Leptonic decay 73% from system anddecay difficult to obtain from first principle ！ the contribution of hadrom Vacuum polarization（　　） obtained from Experimental Data. Cross section of Hadron system Hadron system decay is useful to determine the term , JPS 2003 in Sendai

  4. mass square spectrum and decay K(s) is known function. Hadron Vacuum polarization term from 2 system ( ) Spectral function is measured in this experiment. JPS 2003 in Sendai

  5. base • base agree within Present status ; Muon Anomalous Magnetic Moment ( ) • Exp. ・・・measured by BNL (g-2) experiment.（2002.9） • Theoretical prediction・・・ new data (CMD-2) and data (ALEPH) （2003.1） difference by ・Hadron Vacuum Polarization. term is different between and base predictions. ・Cross check is important ! JPS 2003 in Sendai

  6. event selection criteria Event selection event selection Data : accumulated from 2000.10 to 2000.12 at Belle. (corresponding to production.) • Number of charged tracks：2 or 4 • All charge ( ) = 0 • event vertex position : • Separate the event into 2 hemisphere by the event axis. • Event axis direction : • Back Ground rejection (next slide) • Physics trigger JPS 2003 in Sendai

  7. Bhabha , and two photon rejection MC Data Missing Mass (GeV) Missing Mass (GeV) Two photon BG Bhabha BG Missing angle Missing Angle Missing Angle • Hadron( ) rejection Missing Mass(MM) • Reject high-multiplicity event ( ) event selection (Back ground rejection) • Missing mass and Missing angle cut ( plot) about 1,300,000 events are remained.

  8. one charged track in hemisphere. • one in the hemisphere. • gamma condition : gamma-like shower shape • : • veto the additional gamma • (with high momentum (more than 200 MeV/c)) selection criteria ＊We do analysis each hemispheres. Event selection JPS 2003 in Sendai

  9. Mass invariant mass distribution resolution of Signal region Side-band region are used for estimation of BG in signal region. 320,000 events. signal Side-band region right： left： JPS 2003 in Sendai

  10. Clear peak of . is dominant. peak. is also included . mass spectraum B.G. fraction JPS 2003 in Sendai

  11. Unfolding Acceptance and bin-by-bin migration effects are corrected via Singular-Value-Decomposition method. acceptance Acceptance include both the tau-pair and pipi0 selection. Mass square resolution : 0.03 GeV2 JPS 2003 in Sendai

  12. Unfolded mass spectrum Red line : Breit Wigner fitting function ( and are included. ) JPS 2003 in Sendai

  13. mass distribution Spectral function Breit Wigner fitting form free parameter Gounaris and Sakurai (G&S) Model GS model is known that it can fit wilder mass region that the commonly used BW. JPS 2003 in Sendai

  14. fit result and compare with previous Experiments • parameters : good agreement with previous Exp. • parameters : Belle results are most precise. JPS 2003 in Sendai

  15. Evaluation of JPS 2003 in Sendai

  16. Systematic error (Ⅰ) External systematics ~Normalization factors~ Largest error from JPS 2003 in Sendai

  17. 1.Non- BG. • 　・estimated by B.G. MC. • ・ control data sample are used • for the calibration. • 2. Feed-across • ・ of measured Br. • 3. Energy scale • ・uncertainty estimated from • mass peak. • Selection • ・estimated from the uncertainty • of side-band. • 5. minimum energy Systematic error (Ⅱ) Internal systematics JPS 2003 in Sendai

  18. Consistent within error excluding common error ( base) result preliminary Result of is … cf. ALEPH JPS 2003 in Sendai

  19. Backup slide JPS 2003 in Sendai

  20. Data from Belle event selection event selection mass spectrum of Data Unfolding(reject detector contribution) decide mass spectrum Spectral function measurement Calculation of the term hadron vacuum polarization Analysis Flow of this analysis JPS 2003 in Sendai

  21. Belle detector Data taking system Raw Data event selection Used Data data accumulated from 2000.10 to 2000.12 at Belle data : event event selection event 2.Event selection Exp. Data Monte Carlo simulation Simulator of event production Detector simulation Data reconstruction JPS 2003 in Sendai

  22. decay to 1 charged track　：　about 85% decay to 3 charged tracks　： about 15% decay event selection • There are few charged tracks in the event. 72% 13% • There are missing of momentum and mass because of neutrino ( ) . missing JPS 2003 in Sendai

  23. Bhabha , and two photon rejection • clean Bhabha and mumu event rejection : Missing angle • Hadron( ) rejection Missing Mass(MM) event selection (Back ground rejection) • Missing mass and Missing angle cut • Low-multiplicity event : Then ,we obtained about 1,300,000 event of . JPS 2003 in Sendai

  24. Missing mass VS. Missing angle Data MC(tau) MC(2photon) MC(Bhabha) JPS 2003 in Sendai

  25. Time dependence of event data at Belle detector is stable within 0.5%. Time dependence JPS 2003 in Sendai

  26. Time dependence of event is stable within 0.5%. Time dependence JPS 2003 in Sendai

  27. Momentum of and Good agreement between Data and MC . JPS 2003 in Sendai

  28. Fitting result of Breit Wigner model K&S model G&S model JPS 2003 in Sendai

  29. Fitting result JPS 2003 in Sendai

  30. Unfolding of invariant mass About Unfolding The observed distribution includes contribution of detector acceptance ,and smeared . We can obtain true distribution by using Unfolding. Unfolding is carried out by Singular Value Decomposition (SVD)method. JPS 2003 in Sendai

  31. Spectral function JPS 2003 in Sendai

  32. MC (two photon) Data Systematic detail 1 (1) BG estimation (two photon ) Two photon B.G. estimated by Data using control sample. (2) BG estimation (hadron) Hadron BG contribution also estimated by Data using control sample. JPS 2003 in Sendai

  33. 2% uncertainty of mass spectrum is assumed. Use control sample of side-band . (5) side-band subtraction Systematic detail2 (3) Energy scale (4) Gamma energy threshold Uncertainty of as gamma-threshold function. JPS 2003 in Sendai

  34. Hadron Vacuum polarization and Data The term of hadron vacuum polarization JPS 2003 in Sendai

  35. Data and Data semi-Leptonic dacayc decay Iso-spin 、Cnserve of Vectro Current We can treat data as same condition as data. JPS 2003 in Sendai

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