Cosmic flux simulation in geant4 (comparison to CRY generator)

Physics Processes, Models and Cross Sections
1

Geant4 Version: 11.4.2
Operating System: Linux Debian
Compiler/Version: 10.2
CMake Version: 3.33.1

Dear all,

I am trying to simulation particle shower at sea level. I did the same (identical) model as it was done in “Monte Carlo Simulation of Proton-induced Cosmic-ray Cascades in the Atmosphere” for CRY cosmic flux generator. My problem is the following:

I think I tried almost all physics packages and several cross section databases (from GEANT 4 Libraries and Download Geant4-11.4.2 - Geant4 (dataset G4TENDL1.4)). And at the sea level I am always obtaing (total numer of electrons(±) / total number of muons(±)) ~ 0.4. But when using CRY generator I always get (total numer of electrons(±) / total number of muons(±)) ~ 0.25. And I cannot understand which result is right. Maybe someone could tell me which number is right. Or maybe I need to use some specific physics lists?

2

I recommend checking the CORSIKA code for the ground-level fluxes. Its output may then be used in a Geant4 simulation.

3

Thank you for answer, yes it is possible. But I want to repeat simulation like it was for CRY. So did’t find the solution yet. Also tried different cuts, and different cuts per region (from 0.0 mm to 1000 m). Different physics lists for electromagnetic and for hadronic. And the result still the same.

4

Probably I found out the solution:

So according to these posts Big differences in muon generation between 11.0.4 and 11.1.1 and Range of low-energy muons changed between 11.0.p0 and 11.2.p01 I downgrade geant4 to version 11.0.4 and apply next command before Initialize.

The main thing is I forced GammaToMuonsFactor to 1e16!!!

UImanager->ApplyCommand(“/physics_lists/em/GammaToMuons true”);
UImanager->ApplyCommand(“/physics_lists/em/GammaToMuonsFactor 1e16”);

After this my ratio electrons to muons now ~0.25 as in CRY and agrees to literature. Energy and angular distribution of muons and electrons are also good!

In my physics list I use:

// EM Physics
RegisterPhysics(new G4EmStandardPhysics_option4());

// Extra
RegisterPhysics( new G4EmExtraPhysics(ver) );

// Decays
RegisterPhysics( new G4DecayPhysics(ver) );

// Hadron Elastic scattering
RegisterPhysics( new G4HadronElasticPhysicsHP(ver) );

// Hadron Physics
RegisterPhysics( new G4HadronPhysicsINCLXX(ver));

// Stopping Physics
RegisterPhysics( new G4StoppingPhysics(ver) );

// Ion Physics
RegisterPhysics( new G4IonINCLXXPhysics(ver));

But actually now it also works with general FTFP_BERT physics list, and result almost the same.

This method doesn’t work in the last geant4 version, but I will test one more time and other versions.

So any comments?