Forward Tracking Simulation

1. Forward Tracking Simulation Norman A. Graf ALCPG Cornell July 15, 2003

2. 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 • Study various readout schemes (pixel, stereo angle) • Hit merging and ghosting important. • Include beam backgrounds • Largest source of hits!

3. 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.

4. 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

5. 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.

6. 1000 Events 500/Event Missed ~250/500,000 (99.95%)

7. Track-Finding Time/Event 500 /event 700MHz PIII

8. 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.

9. 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.

10. Single Beam Crossing

11. Single Beam Crossing

12. Hit Densities vs. Radius SD T. Maruyama

14. 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.

15. 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!

16. 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?

17. Tiling Forward Disks

18. Shallow Angle Stereo Large Angle Stereo Strip Orientations

19. 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.

20. Summary • 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.