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Re: How to merge two LCIO events [message #1070 is a reply to message #1047] Thu, 06 September 2007 12:42 Go to previous messageGo to previous message
killenberg
Messages: 125
Registered: July 2005
Location: CERN
Hello,

I would like to point out that merging events is not that simple with a TPC. This is due to the fact that the third coordinate which is measured is time. So one has to take into account the drift velocity and (temporal) bunch spacing to calculate the correct time where the TPC sees the hit. One also has to keep in mind that the TPC only takes one large picture of the whole bunch train and one has to disentangle later which track belongs to which event.

To calculate the occupancy (which I suppose is the reason why you want to overlay events) one further has to take into account the readout frequency and the diffusion in the gas to calculate the correct number of occupied voxels.

In my opinion it does not make much sense to simply merge SimTrackerHits from different events for a TPC, since one can only obtain reasonable tracks if one bypasses major parts of the digitisation and reconstruction and more or less directly fits the track to the SimTrackerHits (maybe with a little smearing). But I doubt that such a simplified ways is suited for an occupancy study.

Track reconstruction efficiency etc. can only be tested if the tracks have the correct 'position' in time, anyway.

The MarlinTPC group has just started working on a pileup processor for the TPC to get a realistic digitisation. Is there a similar solution available in Java?

Greetings

Martin


Martin Killenberg

CERN
martin.killenberg@cern.ch
 
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