Add a random stream specific for ionisation and scintillation calculations in LArG4
Currently, ionisation and scintillation (IS) calculations draw random numbers from the Geant4 stream.
This means that when IS model is changed or tweaked, Geant4 propagation is also affected.
#2 Updated by Gianluca Petrillo over 3 years ago
This has been noticed while studying the effects of solution of issue #16344.
It turns out that
G4Poisson(mean) to get the number of observed photons.
G4Poisson() internally uses one of two different algorithms, depending of
mean value, which extract a different number of random numbers (1 or 2).
The random stream Geant4 uses for the propagation through matter is the same that
G4Poisson() uses, therefore a change in number of scintillated photons can directly affect Geant4 results.
OpFastScintillation is not part of Geant4.
#5 Updated by Hans-Joachim Wenzel over 2 years ago
In the refactored larg4 the ionisation and scintillation calculations are not done in the geant4 module anymore but they are the first step in the module that calculates the drift of electrons to the wire using the SimEnergyDeposit data product as input. There for the state of the random numbers in geant 4 is not affected.