Home » PANDA » PandaRoot » EMC » Geant3 tracking cuts for the EMC
|
|
|
|
|
|
 Re: Geant3 tracking cuts for the EMC [message #9566 is a reply to message #9562] |
Fri, 16 October 2009 15:10   |
StefanoSpataro
Messages: 2736
Registered: June 2005
Location: Torino
|
first-grade participant |
From: *to.infn.it
|
|
Hello,
I am not surprised about the energy difference, but I am much more surprised about the crystal multiplicity. I mean, after digitization and the cut in energy of each single crystal, the numbers should converge.
About the "tuned cuts" , one needs real experimental data to understand what is good for simulation... still too early, we cannot do yet geant validation (or at least, not from the data sets I have seen, and without passive materials).
Maybe you could try to see the difference between G4 without cuts, G4 with 1 MeV cut and G3 with cut, to evaluate the systematic error within simulation. However, this should affect only shower shape analysis (and pi0 recognition for different digi mult), not the energy response (hopefully).
|
|
|
|
|
|
|
|
|
|
| Re: Geant3 tracking cuts for the EMC [message #9571 is a reply to message #9568] |
Fri, 16 October 2009 17:36 |
Jens Sören Lange
Messages: 193
Registered: June 2005
|
first-grade participant |
From: *physik.uni-giessen.de
|
|
| Bertram Kopf wrote on Fri, 16 October 2009 15:25 |
... range cuts instead of fixed energy cuts (at least for G4). I think that such cuts are more reasonable and more convenient for tuning the parameters with real data in the future.
Cheers,
Bertram.
|
Hi Bertram,
here I have a different opinion.
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 also think that "1 mm range cut" gives just one possible result (e.g. for cluster energy), but nobody can say if it gives the correct result or not. Only the comparison to G3 or prototypes (and getting consistent results) can tell us which is the correct result. There was quite some discussion about this when we found the singificant differences between G3 and G4. See e.g.
http://panda-wiki.gsi.de/cgi-bin/view/Computing/Minutes06May2008
http://panda-wiki.gsi.de/cgi-bin/view/Computing/Minutes13May2008
cheers, Soeren
P.S. the equivalent energy threshold values in your table are order of 0.1 eV or even finer, which is most probably too fine for tuning anyway.
|
|
|
|
|
|
|
|
| Re: Geant3 tracking cuts for the EMC [message #9582 is a reply to message #9562] |
Mon, 19 October 2009 15:29 |
Mohammad Al-Turany
Messages: 518
Registered: April 2004
Location: GSI, Germany
|
first-grade participant |
From: *dip.t-dialin.net
|
|
Hi,
One should differentiate between production cuts (Geant3) and tracking cuts in G4! So you cannot simply compare the two! Anyway Geant4 uses the mm cuts, and in the VMC the energy cuts are translated to mm cuts internally but they are applied as tracking cuts, i.e. particle loses energy by generation of secondaries down to an energy corresponding to the range cut, then the particle is tracked down to zero energy using continuous energy loss. To summarize, the range cut-off represents the accuracy of the stopping position. It does not mean that the track is killed at that energy like in Geant3. (see Geant4 Physics Reference Manual)
And if you look at the output in a G4 simulation session you will see the cuts applied in mm for all particles, by default this is 1 mm, one can also change this but this is not the subject of the discussion.
In fact the 1 MeV cut in PandaRoot is too high for the calorimeter, and one should go down with the energy cuts for sure, but this should be done on the EMC level and not globally otherwise the simulation will take ages. To do this one should implement (over-write) the method FairDetector::SetSpecialPhysicsCuts() in the EMC, in this method you have to set:
//for electrons
gMC->Gstpar(MediumId,"CUTGAM",cutE);
gMC->Gstpar(MediumId,"CUTELE",cutE);
gMC->Gstpar(MediumId,"BCUTE" ,cutE);
gMC->Gstpar(MediumId,"BCUTM" ,cutE);
// for hadrons
gMC->Gstpar(MediumId,"CUTNEU",cutH);
gMC->Gstpar(MediumId,"CUTHAD",cutH);
gMC->Gstpar(MediumId,"CUTMUO",cutH);
gMC->Gstpar(MediumId,"PPCUTM",cutH);
MediumId is the medium Id for the material you want to set its property, this you can get usually by:
MediumID = gGeoManager->GetMedium("YourMediumName")->GetId();
cutE and cutH are your favorite cuts.
These are the parameters which one usually uses for calorimeter simulation in G3, and thanks to the VMC this is also valid for G4.
Just a final remark, even though it is possible to use range cuts in native G4 format I would not encourage at all. Because it will be valid only for G4, and it will be hard to convert to energy! On the other hand the energy cuts are valid and more logical for all! G3/G4 and fluka.
Hope this will help!
P.S.
In the newest G4 it is possible to use energy cuts instead of the range cuts, even without the VMC!
Mohammad
|
|
|
|
Goto Forum:
Current Time: Mon Apr 07 05:09:13 CEST 2025
Total time taken to generate the page: 0.00815 seconds
|
GSI Forum
Search
Help
Members
Login
Home
