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Forward Tracking Simulation. Norman A. Graf ALCPG Cornell July 15, 2003. Overview. Develop track-finding strategies for the forward disk regions in SD. Detectors and support material defined. Ideal MC hits written out. Detector digitization post facto

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forward tracking simulation

Forward Tracking Simulation

Norman A. Graf

ALCPG Cornell

July 15, 2003

  • Develop track-finding strategies for the forward disk regions in SD.
  • Detectors and support material defined.
  • Ideal MC hits written out.
  • Detector digitization post facto
    • Study various readout schemes (pixel, stereo angle)
    • Hit merging and ghosting important.
  • Include beam backgrounds
    • Largest source of hits!
tracking strategy
Tracking Strategy
  • Find tracks in the 5-layer CCD pixel VXD, extrapolate forward to pick up hits in the disks.
  • Conformal mapping of 3D hits simplifies pattern recognition.
  • Find tracks from outer radius in, fit, then extrapolate fitted track outwards.
  • Use Kalman filter to reconcile track hit prediction with measured strips.
tracking in vxd
Tracking in VXD
  • Pattern recognition for well-measured, separated 3D points is not a problem.
  • Five layers provide sufficient redundancy.
  • Test pattern recognition in simplified events
    •  events: 1, 10, 100, 200, 500 /event
    • 3, 5
    • 4 <  < 176
    • 1GeV < E < 10GeV
pattern recognition
Pattern Recognition
  • Conformal-mapping technique applied to 3D hits in VXD and forward disks.
    • Hits smeared by expected resolutions:
      • 5 in r and z for CCD
      • 7 in r and r for FWD
    • No hit merging!
    • No ghosts!
  • Treat as combined system:
    • Find VXD+FWD tracks in forward region.
1000 events 500 event
1000 Events 500/Event

Missed ~250/500,000 (99.95%)

track finding time event
Track-Finding Time/Event

500 /event


hit merging in vxd
Hit-Merging in VXD
  • Currently record exact position of MC track’s intersection with sensitive volume in simulations.
  • Smear with expected measurement resolution
    • Default is 5 microns.
  • Hits are currently distinct, even when they are within a pixel (20 microns!).
  • Real hits populate ~2×1 set of pixels.
  • SLD experience being studied.
adding backgrounds
Adding Backgrounds
  • Backgrounds arising from pairs hitting the beampipe have been generated and passed through the full simulation packages.
  • One can overlay such events from an arbitrary number of beam crossings onto signal events.
vxd tracking
VXD Tracking
  • Systematic investigation of pattern recognition in presence of full backgrounds not yet completed, but no problems experienced yet.
  • Effects of hit-merging to be studied.
    • not expected to be a major factor.
  • Efficiencies and resolutions as a function of  and momentum being compiled.
forward tracking
Forward Tracking
  • Extrapolate found tracks to hit strips.
  • Associate strip hits (either double-sided or back-to-back single-sided) in wedges of z-disks to form 3D space points.
    • Need systematic study of occupancies for various designs.
    • Can we survive the ghosts? Grow as ~n2!
  • Use pixel hits if available.
  • Detailed hit merging and ghosting needed!
forward disk detectors
Forward Disk Detectors
  • Many open issues:
    • Tiling of disks with wafers:
      • Phi segmentation?
      • Radial segmentation?
    • Mix of Si pixel and -strip detectors?
    • If pixel, APD or CCD?
    • If -strip, double-sided or back-to-back?
    • Strip orientations within wedges.
      • Shallow- or large-angle stereo?
next steps
Next Steps
  • Currently developing flexible tools to study effects of disk tiling and strip orientations.
  • Will start characterizing various detector layouts in terms of efficiencies and resolutions.
  • Continue with impact on physics channels of interest for forward regions.
  • Strategies being implemented to handle pattern recognition in the forward regions.
  • Detector digitization infrastructure (hit merging and ghosts) is almost in place.
  • Recognize that detector design requires reconstruction input.

Aim for flexible framework to allow iteration.