1 / 31

ALEPH Results on  Branching Ratios and Spectral Functions

ALEPH Results on  Branching Ratios and Spectral Functions. Michel Davier Laboratoire de l’Accélérateur Linéaire, Orsay. Tau Workshop 2004 September 1 4 - 17 , 2004, Nara , Japan. davier@lal.in2p3.fr. Final ALEPH Analysis.

keenan
Download Presentation

ALEPH Results on  Branching Ratios and Spectral Functions

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. ALEPH Results on  Branching Ratios and Spectral Functions Michel Davier Laboratoire de l’Accélérateur Linéaire, Orsay Tau Workshop 2004 September 14 - 17, 2004, Nara, Japan davier@lal.in2p3.fr M. Davier – ALEPH  Results

  2. Final ALEPH Analysis • only 91-93 data published for  branching ratios, 91-94 for spectral functions • 94-95 statistics x1.5 91-93 • selection efficiencies obtained from data for each topology • improved photon ID  better separation between good and fake photons • new method to correct the number of fake photons (hadron interactions in ECAL • and splitting of EM showers) in MC simulation • reduced feedthrough in low BR channels • improved methods for the estimation of systematic uncertainties Final analysis of the complete LEP 1 data sample Detailed publication available shortly M. Davier – ALEPH  Results

  3.  Event Selection and non- Background •  events selected by vetoing backgrounds • total energy: Bhabhas, -pairs • pT balance, low visible energy: -induced processes • high multiplicity: Z  qq • Break-mix method to determine efficiency on data for every selection cut • tag one hemisphere to get sample unbiased/cut • keep opposite hemisphere as unbiased  decay • construct event sample with pairs of selected hemispheres • apply cut and measure efficiency (small correlations taken from MC) •  event selection efficiency 79% (92% in polar acceptance, 5% / modes) • Non- background measured on data sample for leptonic channels, • from MC for hadronic channels (-induced, 4-fermion, qq) •  kept relatively high (1.2%) to retain large  efficiency M. Davier – ALEPH  Results

  4. Photon ID Collimated  decays  granularity - transverse: 75,000 ECAL cells - 3-fold longitudinal segmentation fake photons data MC good  Likelihood method  probability to be a good photon, discriminating variables to distinguish good/fake photons Large improvement compared to published results on 91-93 data M. Davier – ALEPH  Results

  5. Decay Classification • e e ID, not in ECAL cracks •   ID, P2 GeV • hadronic channels • - 0 reconstruction: 2 resolved photons + kimenatic fit • merged photons (energy-weighted moments) • single photons (single,radiative, collinear; fake) • - track (1 - 2,3,4 – 5) and 0 (1 – 4 for 1-pr, 1 – 3 for 3-pr ) multiplicities • - low BR channels: 3 tighter tracks required for 3h 2-3 0, only resolved • 0’s for h 4 0 and 3h 3 0 • ‘garbage can’ for rejected hemispheres (‘class 14’) 3.6% • e in cracks: 21%  with P2 GeV: 27% • 1-pr hadronic (mostly P2 GeV): 41% • 3,5-pr hadronic: 11% M. Davier – ALEPH  Results

  6.  Sample M. Davier – ALEPH  Results

  7. Global BR Analysis M. Davier – ALEPH  Results

  8. Systematic Uncertainties • method: identify sources of systematics, for each one • - link systematic source to relevant variables • - study data/MC distributions of these variables • - characterize and measure systematic bias  stat error  syst error • - correct MC for measured bias and keep total error as quoted syst uncertainty • main sources • -  / 0 reconstruction • - non- backgrounds • - event selection efficiency • - particle ID efficiency matrix • - secondary interactions • - tracking • - MC dynamics • - MC statistics M. Davier – ALEPH  Results

  9.  / 0Systematic Sources • efficiency at low-energy (threshold) • efficiency at high energy (track overlap) • conversions • rate • h misID in multiprong environment • p misID in secondary interactions • ID efficiency (good/fake probability) • fake photon rate correction • - energy calibration • 0 efficiency • Dalitz decays • - radiative photons M. Davier – ALEPH  Results

  10. Systematic Errors 94-95 (B in %) M. Davier – ALEPH  Results

  11. Particle Spectra (leptons) Data/MC comparison non- background M. Davier – ALEPH  Results

  12. Particle Spectra (hadrons) Data/MC comparison M. Davier – ALEPH  Results

  13. Mass spectra Data/MC comparison All multihadrons h 0  feedthrough non- M. Davier – ALEPH  Results

  14. Exclusive BR‘s • topological BR’s defined by charged-track and 0 multiplicities • class 14 (removed decays) consistent with 0 • B14 = (0.065  0.027  0.028) % • consistent with  standard decays • dedicated analysis found no ‘invisible’ decay (efficiency=0 in our selection) • Binvisible  0.11% (95% CL) •  assume that all considered modes add to 100% and proceed to • the determination of exclusive BR’s • modes with kaons (KS, KL, K) have been measured separately • (complete study with full LEP 1 ALEPH data up to 4 hadrons/mode), • subtracted on a statistical basis • correct for EM modes (all  decays,  , 0) using measured • channels with  and  M. Davier – ALEPH  Results

  15. Non-strange Branching Ratios M. Davier – ALEPH  Results

  16. Leptonic modes ( ) ( ) M. Davier – ALEPH  Results

  17. Hadronic modes (1-prong) M. Davier – ALEPH  Results

  18. Hadronic modes (3,5-prong) M. Davier – ALEPH  Results

  19. Lepton Universality in the Charged Current Be and B g / ge = 0.9991  0.0033 Be , B and  WA (290.6  1.1) fs g / g = 1.0009  0.0023  0.0019  0.0004 g / ge = 1.0001  0.0022  0.0019  0.0004 (Be , B)()(m) B and  WA g / g = 0.9962  0.0048  0.0019  0.0004  0.0007 (radiative corrections) Beuni = (17.810  0.039) % M. Davier – ALEPH  Results

  20. The Hadronic Sector CVC + isospin breaking eeALEPH B0 24.52  0.31 25.47  0.13 0.95  0.33 (%) B30 1.09  0.08 0.98  0.09 -0.11  0.12 B30 3.63  0.21 4.59  0.09 0.96  0.23 a1 decays B3 / B20 = 0.979  0.018 to be compared to 0.985 CLEO (PWA + isospin breaking /  masses) V,A separation R = 1  Be – 1.9726 = 3.642  0.012 R,S = 0.160  0.006  R,V+A = 3.482  0.014 R,V = 1.782  0.011  0.002 R,A = 1.700  0.011  0.002R,VA = 0.081  0.018  0.005 M. Davier – ALEPH  Results

  21. Spectral Functions • hadronic mass spectra corrected by kinematic factor and scaled by Bi  Be • unfolding from detector effects by regularized inversion of 140x140 detector • response matrix (Höcker-Kartvelishvili) • specific systematic studies using full analysis for every syst. source, • constructing corresponding covariance matrices • -  and 0 reconstruction • - energy calibration and resolution (charged particles and 0‘s) • - tracking and secondary interactions • - unfolding procedure (test distributions) • spectral functions obtained for the leading channels 0, 20, 30, • 3, 30 M. Davier – ALEPH  Results

  22. Spectral Functions: Results M. Davier – ALEPH  Results

  23. Spectral Functions: V, A A V M. Davier – ALEPH  Results

  24. Spectral Functions: V  A V  A V + A M. Davier – ALEPH  Results

  25. Spectral Functions: QCD analysis • changes since 1998 published analysis: full LEP1 statistics for BR • re-analysis of spectral functions • analysis now even more limited by theoretical uncertainties • some progress in the calculation of the S4 term (Chetyrkin-Kühn et al) • but not complete yet: favours Kataev-Starshenko estimate K430 • use R,V, R,A, R,V+A, and the mass-weighted moments (shapes) • results soon available • - very close to published ones with smaller experimental and slightly • smaller theoretical errors • - some evidence for OPE problems, except in the V+A case where • it does not matter (non-perturbative contributions below 1%) • recall published results S(m2) = 0.334  0.007exp  0.021th • S(MZ2) = 0.1202  0.0008exp  0.0024th  0.0010ext • from Z width (EW fit) S(MZ2) = 0.1183  0.0027 M. Davier – ALEPH  Results

  26. The Complete List of ALEPH Branching Ratios M. Davier – ALEPH  Results

  27. Backup Slides M. Davier – ALEPH  Results

  28. ––0: Comparing ALEPH, CLEO, OPAL Shape comparison only. SFs normalized to WA branching fraction (dominated by ALEPH). • Good agreement observed between ALEPH and CLEO • ALEPH more precise at low s • CLEO better at high s M. Davier – ALEPH  Results

  29. 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! M. Davier – ALEPH  Results

  30. New Precise e+e–+– Data from KLOE Using the „Radiative Return“ Overall: agreement with CMD-2 Some discrepancy on  peak and above ... ... M. Davier – ALEPH  Results

  31. The Problem (revisited) Relative difference between  and e+e– data: zoom No correction for ± –0 mass (~ 2.3 ± 0.8 MeV) and width (~ 3 MeV) splitting applied Davier, hep-ex/0312064 Jegerlehner, hep-ph/0312372 M. Davier – ALEPH  Results

More Related