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Re: Geant3 tracking cuts for the EMC [message #9578 is a reply to message #9571] Mon, 19 October 2009 12:00 Go to previous messageGo to previous message
Christian Hammann is currently offline  Christian Hammann
Messages: 24
Registered: July 2009
Location: Bonn
continuous participant

From: *cb.uni-bonn.de
Hi Soeren

Jens Soeren Lange wrote on Fri, 16 October 2009 17:36


I think experimentally (for "real data") it is really much easier to set threshold (e.g. discriminator) to energy (e.g. 1 MeV) and not to a particle range (e.g. 1 mm). In fact, so far we were (e.g. for the EMC) always talking about 1 MeV threshold or 3 MeV threshold or whatever value, but never about "threshold of 5 mm for a e-, but 3mm for a pi+ (in the same crystal)".



I think I have to agree with Bertram that the 1mm cut in geant 4 is more convienient for the EMC.
The energy cut in geant3 does not in any way correspond to the threshold which is set in the discriminator (in the case of the EMC). The cut applies to the individual particles in the shower, which are tracked or not depending on their energy. In the EMC only the sum of their energies is measured, no threshold can be set for individual shower particles. Thus this cut is more like a range cut, as with lower cut values more particles are propagated and more energy can be transported to the edge of the shower.

This can be seen in the example I gave above, by lowering the cut value the energy in the central crystal decreased by 30MeV!

The range cut in geant4 simply says you don't care whether the energy is deposited here or in 1mm distance. That's the case for the EMC: one doesn't care where in the crystal you have the energydeposition as long its in this crystal. That simply means the cut distance has to be much smaller than the size of the crystal (of course this has to be tuned).

Best regards
Christian



Christian Hammann
Universität Bonn
Helmholz-Institut für Strahlen und Kernphysik
Nußallee 14-16
53115 Bonn
Tel: +49 228 733895
Fax: +49 228 732505
 
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