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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.

Hit densities vs radius
Hit Densities vs. Radius


T. Maruyama

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?

Strip orientations

Shallow Angle Stereo

Large Angle Stereo

Strip Orientations

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.