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Charge Mapping in SCT_Digitisation

Charge Mapping in SCT_Digitisation. SCT Digitisation Task Force Meeting. 7 th September 2010. Richard Batley. (Cambridge). Single muons with full (GEANT4) sim / digi / reco :. -- standard SCT_Digitisation. -- vs 1 m m charge map provided by Taka.

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Charge Mapping in SCT_Digitisation

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  1. Charge Mapping in SCT_Digitisation SCT Digitisation Task Force Meeting 7th September 2010 Richard Batley (Cambridge) Single muons with full (GEANT4) sim / digi / reco : -- standard SCT_Digitisation -- vs 1mm charge map provided by Taka Compare efficiency / bias / resolution for -- SCT barrel clusters -- reconstructed charged tracks

  2. Single Muon Samples Three fully-simulated samples : -- pT = 100 GeVm-, 1 GeVm-, 1 GeVm+ ; |h| < 1 -- start point (x,y,z) = (0,0,0) -- inner detector only -- Athena 15.8.0.2 (GEANT4.9.3) -- ATLAS-GEO-10-00-00, OFLCOND-SIM-BS7T-00 -- 20k events (single muons) per sample Two digitisation models (run on identical G4 hits) : -- standard SCT_Digitisation-00-12-10 (red) -- 1mm charge map from Taka (blue) (via private hack of SCT_Digitisation-00-12-10) (slightly different Vbias and Temp ??)

  3. Reconstructed clusters dashed : all SCT barrel clusters solid : associated to a “clean” primary muon G4 hit ( |Dx| < 0.2mm ) all samples combined (60k single muon events) red : current model blue : charge map all m±

  4. Compare reconstructed and true cluster positions (local-x) : -- take true cluster position from G4 hit = average of true wafer entry and exit points (after chaining G4 hits together if necessary) -- use only “clean” G4 hits from the primary muon : - entry and exit points at least 1mm from wafer edge - and at least 1mm from central bond-gap 7.74 100 GeVm- = mean number of clean primary hits per event : 1 GeVm- = 7.95 1 GeVm+ = 7.56 -- look only at nearest cluster to true hit in local-x : Dx ≡ xlocal(cluster) – xlocal(true G4 hit)

  5. Distance to nearest reconstructed cluster : all m- 100 GeV m+ 1 GeV m- 1 GeV

  6. Same, but zoomed in and with linear y-axis : all m- 100 GeV m+ 1 GeV m- 1 GeV

  7. Cluster inefficiency Define “inefficient” as : no cluster within |Dx|<1mm of a clean primary muon G4 hit all (compute f angle from G4 hit, not from reconstructed track)

  8. Includes inefficiency due to dead SCT modules in MC : (need to find out how to remove them) all all  higher inefficiency for charge map for central tracks ? (need to check that this is not a bug/feature of the charge map implementation in SCT_Digitisation)

  9. Cluster width for clusters within |Dx|<0.2mm of a clean primary muon GEANT4 hit all m- 100 GeV m+ 1 GeV m- 1 GeV

  10. Cluster position resolution = raw rms of Dx distribution for |Dx| < 0.1mm all

  11. Cluster position bias = mean of Dx distribution for |Dx| < 0.1mm dashed : side 1 solid : side 0 all → small shift of spacepoints in z-direction

  12. Reconstructed tracks Total no of reconstructed tracks in 60k events : 59992 59991 all all Avg no of SCT barrel hits on track : 8.31 8.30 100 GeVm- : 1 GeVm- : 8.49 8.48 1 GeVm+ : 8.10 8.08

  13. reconstructed track d0 : all m- 100 GeV m+ 1 GeV m- 1 GeV

  14. reconstructed track z0 : all m- 100 GeV small z0 shift m+ 1 GeV m- 1 GeV

  15. Summary Charge mapping can be implemented in SCT_Digitisation with only minor changes to the existing software (but impact on CPU and memory would need study) Initial study of charge map with single muons very similar output to current digitisation model  but suggests some small differences : -- slightly higher cluster inefficiency -- slightly narrower clusters at low pT / large angle → slightly larger position resolution -- smaller cluster position bias, of opposite sign → small shift in z0 at high pT

  16. BACKUP SLIDES

  17. Induced Charge Model (ICM) maps Maps available (so far) from Taka : Vbias = 150 V, Vdep = 65 V T = 0oC 1) Pulse map -- 5mm grid, Dt = 1ns [5] : strips -2, -1, 0, +1, +2 [17] : 0, 5, 10, ..., 80 µm Pulse[5][17][57][50] [57] : 2.5, 7.5, ..., 282.5 µm [50] : 0, 1, 2, ..., 49 ns map electronics response vs time for point charges  (including crosstalk as in current SCT_Digitisation) 2) Charge maps -- 7.5, 5.0, 2.5, 1.0mm grids, Dt = 0.5ns Charge[5][11][38][50], ... , Charge[5][81][285][50] map induced charge vs time for point charges  Use linear interpolation between nearest grid points

  18. Induced charge profiles for point charges (examples) : strip -2 strip -1 strip 0 strip +1 strip +2 (x,y) = (5,20) (x,y) = (40,250) Map = piecewise linear interpolation with Dt = 0.5 ns (too coarse ?)

  19. Effect of cluster position bias Layers 0, 2 2 mm 2 mm ~ 100 mm Layers 1, 3 2 mm 2 mm small systematic shift Dz (spacepoint)> 0 ?

  20. Cluster bias  Track parameter bias SCT pixels

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