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Update on Fragmentation Function Analysis Components from LEP1 - DELPHI QCD Meeting, Dec 2000

This document presents an update from the DELPHI collaboration on the analysis of fragmentation function components at LEP1, focusing on data collected between 1992 and 1995. Key components, selection cuts, and correction factors for detector acceptance, secondary interactions, and kinematic constraints are detailed. The study reveals significant fragmentation effects and introduces algorithms to compensate for these at low momentum fractions. The findings are based on data from over 20 million events, leading to refined cross-sectional measurements and insights into the fragmentation process in high-energy particle collisions.

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Update on Fragmentation Function Analysis Components from LEP1 - DELPHI QCD Meeting, Dec 2000

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  1. DELPHI week QCD Meeting 5 December 2000 Update on the analysis of fragmentation function components at LEP1 Oxana Smirnova Christina Zacharatou Jarlskog Thanks for suggestions to: Torbjörn Sjöstrand

  2. Components of the Fragmentation Function at Q = 91.2 GeV

  3. Cuts for charged particles: Rf impact parameter < 5 cm z impact parameter <10cm/sinq track length > 50 cm 0.1 GeV < p < 50 GeV 11o < q <169o Dp/p < 100% Cuts for events: at least 5 tracks with p>0.2 GeV total energy > 15 GeV Ehem > 3 GeV 26o < qsphericity < 154o max pimbalance = 20 GeV Data Selection

  4. Raw Data Binning: • 40 channels in cosq • 22 channels in xp: - 10 bins of width 0.01 - 5 bins of width 0.02 - 2 bins of width 0.05 - 3 bins of width 0.1 - 2 bins of width 0.2

  5. Correction Factors Correction factors for detector acceptance and resolution, isr, secondary interactions and kinematic cuts: Track and event selection cuts as in data.

  6. Corrected Cross Sections (in 22 xp bins) For each bin: Combined data for all years:

  7. Extraction of fragmentation function components Weighting method

  8. Components by weighting

  9. Components by weighting and fitting (only statistical errors)

  10. The fragmentation effect 20 M events from Jetset7.4: • no shower • only 2-jet events

  11. A simple algorithm to compensate for the fragmentation effect • estimate hadron-quark angle from Jetset (no shower) • use estimate to smear hadron polar angle • fit data using smeared distributions

  12. FT from the algorithm

  13. FL from the algorithm

  14. c2 from the algorithm

  15. Summary • Analysis updated for 1992-1995 data at Z peak • Study with Jetset shows non-zero FL in the absence of gluons: attributed to the fragmentation effect • Algorithm implemented to estimate compensation: FL reduced significantly at xp below 0.1 • More factors to be taken into account...

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