| Summary: | Shift in TestEm3 calorimeter energy when using opt2 and G4GammaGeneralProcess | ||
|---|---|---|---|
| Product: | Examples/Extended | Reporter: | Michele Veltri <michele.veltri> |
| Component: | electromagnetic/TestEM0-4. 11-18 | Assignee: | Vladimir.Ivantchenko |
| Status: | RESOLVED FIXED | ||
| Severity: | minor | CC: | michel.maire |
| Priority: | P4 | ||
| Version: | 10.7 | ||
| Hardware: | All | ||
| OS: | All | ||
| Attachments: | DelteE-GammaGenProc(ON - OFF) of calo energy in lead and scintillator as a function of the e- beam energy | ||
Hello Michele, I have tried TestEm3 using the new Geant4 version 11.2, which will be publicly available December,8 2023. In the test Lead/Sc structure was used from lhcb.mac file, cut value was set to 0.7 mm. The results are following: PhysList GGP E(GeV) Esc(GeV) RMSsc(MeV) ---------------------------------------------------------- EM Opt0 yes 1 0.16987 +- 0.00013 12.91 +- 0.13 EM Opt0 no 1 0.16993 +- 0.00013 13.08 +- 0.13 EM Opt0 yes 10 1.7007 +- 0.0004 41.83 +- 0.42 EM Opt0 no 10 1.7013 +- 0.0004 41.51 +- 0.42 EM Opt0 yes 100 16.991 +- 0.002 185.8 +- 1.9 EM Opt0 no 100 16.912 +- 0.002 173.0 +- 1.7 ---------------------------------------------------------- EM Opt2 yes 1 0.12793 +- 0.00012 11.88 +- 0.12 EM Opt2 no 1 0.12792 +- 0.00012 12.0 +- 0.12 EM Opt2 yes 10 1.2822 +- 0.0004 38.14 +- 0.38 EM Opt2 no 10 1.2833 +- 0.0004 38.0 +- 0.38 EM Opt2 yes 100 12.77 +- 0.0015 146.5 +- 1.47 EM Opt2 no 100 12.773 +- 0.0017 171.4 +- 1.71 ---------------------------------------------------------- So, for G4 11.2 mean energy deposition in scintillator both Opt0 and Opt2 are very stable and I cannot confirm your plot. There is however an effect for RMS for 100 GeV. My interpretation of this effect - RMS may be biased by outliers - it is usually enough to have one event with very different energy deposition due to high leak or due to absence of high leak, because RMS is computed directly and not obtained from a fit. To understand the problem better I would suggest two things: 1) check lhcb.mac for you case and try to get the same table with G4 10.7.3. 2) try to repeat with G4 11.1.3 3) when 11.2 will be available try again Vladimir Thanks to Mihaly Novak, the problem is fully understood.
The problem reported a shift in the energy deposit distributions using TestEm3 with Geant4-10.7.p03 between activating/de-activating the gamma-general process in case of using the standard EM-opt2 constructor.
The problem is:
• we set the step-function for energy loss processes with dRoverRange=0.8 and finalRange=1.0 mm
at the construction of the EM-opt2 constructor
• then these are actually reset to their default 0.2, 1.0 values in Geant4-10.7.x when activating the Gamma-general process in the G4EmParameters
This causing a shift in the energy deposit distribution, actually not because the Gamma-general process but because the different step function parameter (`dRoverRange=0.8` vs `dRoverRange=0.2`).
The easiest way to resolve is to reset the original dRoverRange=0.8 value of the EM-opt2 constructor after activating the gamma general process with the 2 UI commands:
# turn ON the gamma general process and reset the original step-function of opt2
/process/em/UseGeneralProcess true
/process/eLoss/StepFunction 0.8 1.0 mm
This do not require to change any codes and the problem is fixed in Geant4-11.0.x. So, the problem is resolved.
VI
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Created attachment 834 [details] DelteE-GammaGenProc(ON - OFF) of calo energy in lead and scintillator as a function of the e- beam energy The energy reconstructed by the sampling calorimeter of TestEm3 is increased in lead and reduced in the scintillator of about the same amount when switching on the G4GammaGeneralProcess. The test has been done with v10.7.3 using option2 for the electromagnetic processes. An electron beam of energies varying from about 1 to 44 GeV is shot in the caloriemter. The shift in the reconstructed energy reaches the value of about 150 MeV at the largest beam energy (see attached picture). The shift is not observed when using option0, in this case the energy values for both materials with G4GammaGeneralProcess on/off agree within ~1 MeV.