In Geant4 the threshold for producing secondaries are expressed in range,
universal for all medium. This range is converted in energy for each kind
of particle and each material. (writeup)
We illustrate here the advantages of this procedure.
Liquid Argon(4 mm)--Lead(4 mm)--Liquid Argon(4 mm)--Lead(4 mm)The incident particle is a ionising particle: proton of 500 MeV.
|Threshold in range||e- Energy in Liquid Argon||e- Energy in Lead|
|1.5 mm||455 keV|| 2 MeV|
On the picture, one can see the delta-rays
produced and travelling in Liquid Argon, while nothing in produced in Lead.
(on purpose the multiple scattering is off, and 1000 events are surimposed)
|G3: DCUTE||Edep in lArg||Edep in Pb||Track length in lArg||Track length in Pb|
|455 keV||2.30 MeV+- 329 keV||13.45 MeV+- 991 keV||8.32 mm+- 1 mm||8.47 mm+- 500 mum|
|2 MeV||2.21 MeV+- 339 keV||13.48 MeV+- 1.03 MeV||8 mm+- 0. mm||8 mm+- 0. mm|
It should be noticed that the relevant physics quantities are quite stable versus the production threshold, both in Geant4 and in Geant3 (see above).
|G4: threshold in range||Edep in lArg||Edep in Pb||Track length in lArg||Track length in Pb|
|1.5 mm||2.17 MeV+- 322 keV||13.06 MeV+- 949 keV||8.37 mm+- 1.04 mm||8.02 mm+- 80 mum|
|0.15 mm||2.17 MeV+- 341 keV||13.15 MeV+- 940 keV||8.83 mm+- 1.28 mm||8.67 mm+- 557 mum|
Changing the threshold by a factor 10 lets the energy deposit unchanged
(as it must be: the energy loss is independant of DCUTE)
and the charged track length variation within 1 percent. (Remember that on the pictures 1000 events are surimposed)
The code of this example is in geant4/examples/extended/electromagnetic/TestEm3 run07.mac