All stereo geometry
stereo angle = 60-150 mrad
Constant stereo drop, RP-R0 = 1.5 cm
Almost square cells with field:sense = 3:1
"small" cells in the inner layers, "big" in the outer ones
The shape of the cells varies along r, z and phi and this is crucial
for the calibration of space-time relations.
They are parametrized in term of:
Cell shape: beta (6 reference cells)
Track crossing angle: phi (36 bins)
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