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Reconstructing the z coordinate of a TPC [message #940] Thu, 28 June 2007 13:40 Go to previous message
Messages: 125
Registered: July 2005
Location: CERN

currently I am working on merging the HitFinderUVic and the HitFinder in the trunk. I found the following problem:

In TPC prototypes the z coordinate is usually calculated as the drift distance (implemented in HitFinder trunk). This is convenient for analyses where for instance the resolution is investigated as a function of the drift distance.
In real TPCs at a collider the origin is certainly located at the vertex, which means at the cathode. Here z is calculated as
z = maximumDriftLength - driftVelocity * driftTime
like implemented in HitFinderUVic.

In my opinion both methods can be useful, depending on the use case. So I am planning to implement a processor parameter CalculateZAsDriftTime, which defaults to 0 and can be set to 1 in case of prototype studies.

What Do you think about it?



P.S.: Jason, you are using the two parameters TPC_zEndplate and TPC_electronics_backend_thickness to calculate the maximal drift distance. Obviously this is the information which you are using/is provided by your simulation.
I found that there is a function called getMaxDriftLength() in gear::TPCParameters, which I would like to use. I don't now if the simulation writes the gear file or also reads it. If the former is the case, would it be possible to also write the maximal drift length to the gear file? In the latter case one just additionally writes it to the gear file and the simulation does not have to be changed at all. One just has to look that the gear file is consistent if created manually, as it is redundant information.

Martin Killenberg

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