[Brahms-dev-l] question on coordinate systems

Hello,

I have a doubt about the way the detector volume class makes 
transformation from global to local. In x and z, I don't think there's any 
problem. But surprisingly, I think there is in y. Let me explain :

I made a simulation using brag. I then converted the geant track to tpc 
tracks in T1, etc. Now, when I apply the standard global tracking modules, 
I get a momentum extremely close to the geant track momentum, and when I 
extrapolate the T1 track to the vertex plane, I get Vx = 0.  So in x,z 
that's fine.  But in y, it's different. I tuned the brag geometry so that 
it reflects the geometry in the DB for a given run. There are offsets in y 
for T1 and T2. Now, when I project back the TPC track of the simulation 
to the vertex plane, I get an offset which is equal to the TPC volume 
offset in y.

My question to the experts : is the translation in y taken into account
when going from local to global ? I haven't checked the relevant brat
classes.

Djam


-- 
Djamel Ouerdane ------------------------------------------o
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