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Minimum Bias Low Pt Tracking

Minimum Bias Low Pt Tracking. W. H. Bell 08/02/2007. Overview. Motivation Recap Low Pt Tracking Objectives Steering reconstruction Track Quality Cuts MBTS Trigger Efficiency Conclusions and Outlook. Motivation. Predictions of dN/d η at LHC uncertain

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Minimum Bias Low Pt Tracking

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  1. Minimum Bias Low Pt Tracking W. H. Bell 08/02/2007

  2. Overview • Motivation • Recap • Low Pt Tracking • Objectives • Steering reconstruction • Track Quality Cuts • MBTS Trigger Efficiency • Conclusions and Outlook

  3. Motivation • Predictions of dN/dη at LHC uncertain • Compare NSD with previous results • Use minimum bias measurement as a Monte Carlo tuning input and for pile-up studies.

  4. LHC Predictions σmb approximately 65mb Integrated luminosity of 10pb-1 => 1012 Events

  5. Minimum Bias Trigger Scintillators 2 segments in η 8 segments in φ 2.0 < η < 3.8 inner η outer η

  6. Recap ε From Generator Truth, requiring a Lvl1 MBTS trigger ε Inelastic non-diffractive Inelastic Double and Single Diffractive

  7. Low Pt Tracking • Tracker is in principle sensitive to soft tracks • Pt = 400 MeV - tracks reach end of TRT • Pt = 150 MeV - tracks reach last SCT layer • Pt = 50 MeV - tracks reach all Pixel layers 50MeV 150MeV 400MeV A.Salzburger - Fatras simulation

  8. Low Pt Tracking: Steering Reconstruction • InDetRecExample provides examples • Implement via modified RecExCommon_topOptions.py • minPT = 75MeV • GlobalChi2Fitter • maxHoles = 1

  9. Track Quality Cuts • |d0| < 50mm • |z0| < 1000mm • Pt > 75MeV • No. Silicon Hits >= 4 (of 11) • No. Pixel Hits >=1 (of 3) • No. of holes <=1 • Χ2/d.o.f <= 6.0 • Primary track: require |d0| < 10mm

  10. Data Selection • Pythia 6.4 @ 14TeV • 50k Inelastic non-diffractive • 50k Inelastic single and double diffractive • Data passed through ATLAS Geant simulation and digitization • Generation of MBTS LVL1 containers • Reconstruction run with low pt tracking settings

  11. Problems • All inelastic non-diffractive jobs crashed • 44% of inelastic diffractive jobs crashed • Known problem within tracking software

  12. Reconstructed Tracks: Pt distribution

  13. Reconstructed Tracks: η distribution

  14. Track Quality Cuts: Pt

  15. Track Quality Cuts: η

  16. Track Quality Cuts: Pt vs χ2/d.o.f

  17. Track Quality Cuts: Pt vs Silicon hits

  18. MBTS Trigger Efficiency: Pt

  19. MBTS Trigger Efficiency: η

  20. Conclusions and Outlook • MBTS trigger requirement has no η bias when looking at low pt reconstructed tracks from inelastic diffractive samples. • Better track reconstruction exit condition needed • Need efficiency and purity plots • Affect of Ks? • Vertex constraint?

  21. Backup

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