Minutes of the Monday Meeting, May 7, 2007.

Rob's Editorial comments are in italics.

When: Monday 1:30 PM
Present: Norman, Caroline, Dima, Hans, Jeremy, Rob, Tim, Jeremy

Candidate goals for this Week

This was copied from the whiteboard:

1. Define classes for tracking infrastructure
   • Flesh out Rob's diagram: http://docdb.fnal.gov/ILC-public/DocDB/ShowDocument
   • Make sure the relevant ideas from existing code are included.
2. Define a cheater for SimTrackHit to whatever it is that is used as input for pattern recognition.
   • Rob will do this once the endpoint is defined.
3. Re: links back and forth between Geometry and TrackerHits
   • Do we need full bidirectionality, as Jeremy has suggested, or is one way enough.
4. Re: Forward geometry.
   • Can Hans present a road map?
5. How does the above affect tracking algorithms?
   • This was written in response to Rob's comments that we need to resolve:
     • Cylindrical vs polyhedral issue.
     • Version control.

Dima's Geometry System

Dima showed some slides that were circulated by email.

The code discussed in these slides is available in: org.lcsim.contrib.onoprien.tracking.*

The original motivation for this code was for calorimeter assisted tracking in the forward region. The code uses both 1D and 2D readout. The code was developed some time ago but he has recently resurrected it.

When Dima wrote this code the geometry system was missing a lot of functionality. So he created it. With the recent work of Tim and Jeremy we have a much more functional geometry system. We now need to understand how to get one system from these two and make sure that it addresses everyone's needs.

Hans asked if this code supports alignment? Answer: it does not but it could.

Dima's code is flexible enough to store either hits on the cylindrical detector or hits on a polyhedral detector.

During the discussion it became clear that the word "Segmentation" was used in 2 different ways by various people in the room:

• The breakdown of a layer into sensors
• The arrangment of pixel/strips on a sensor
  The was lots of confusion when the speaker used segmentation in the second sense and some listeners assumed it was the first sense.

Aside: Another word that was used during the discussion, but not in Dima's talk, is "virtual segmentation". In this usage, segmentation is real if an object exists in the geometry system for each segment; for example there is an object to represent each wafer, about 10,000 to 20,000 in the vertex+tracking detectors. This, however, is not a practical solution for representing indvidual strips and pixels as there are too many of them. Instead there are objects that can compute which pixels or strips are hit given the intersection of a track with a silicon wafer; lists of hit strips and pixels are kept. This is refered to as virtual segmentation.