CSC global

1
CSC global local coordinates
2
A list of clusters and associated strips
Layer 1
Global positions
Layer 2
Layer 3
Layer 4
Strips 60 of each layer are at the same global
position for ALL layers
3
Why?

• There is only one common surface defined for
  every layer in CscRdoToCscPrepData.cxx
• This surface is the center of the CSC module
• All local coordinates are projected onto this
  surface for local-gtglobal transformations
• Solution ? In CscRdoToCscPrepData.cxx
• From
• const GlobalPosition globalWirePos
  descriptor-gtsurface().localToGlobal(
  localWirePos )
• To
• const GlobalPosition globalWirePos
  descriptor-gtsurface(channelId).localToGlobal(
  localWirePos )

4
global lt-gt local transformations

• As the axis passing by the chamber center and
  orthogonal to the chamber entrance plane do no
  point to the origin (0,0)
• An effective rotation of 0.266 degree is applied
  at center
• Vary with depth (layer) inside module
• See next slide

5

• Amdb
• axis normal to CSC entrance plane
• ?chamber center is 35.517mm down

CSC Transverse View
Points to (0,0)
Points to (0,0)

• Geomodel
• Axis normal to CSC entrance plane
• crosses at chamber center
• This axis is used for .transform it is wrong

Does not Point to (0,0)
6
Consequence/solution?

• Global-gtLocal transformation wrong up to 200
  microns
• CscRdoToCscPrepData.cxx, CscThresholdClusterBuilde
  r.cxx and some others have to be modified,
• Alternatives
• Surfacecenter shifted by 35.517mm
• Surfaceplane rotated according to position in
  depth?
• 1. Looks the simplest?
• The GeoModel looks OK.