Strange behavior of muon pairs photoproduction cross section in Geant4 11.2 version

Physics Processes, Models and Cross Sections
1

Hi,

I am trying to produce muon pairs from photons (photon energies of 4.4 GeV) using latest version of GEANT4 11.2 on lxplus. I use the standard “FTFP_BERT” physics list. I used the following commands for activating the muon photoproduction process

/physics_lists/em/GammaToMuons true
/physics_lists/em/GammaToMuonsFactor 1000 (or 1 or 100)

1. Changing the factor did not give any change in muon pair yield. It seems the factor is not doing anything?
2. For low 300 MeV photons I get much more muon pairs without biasing (using Factor =1).

I have done similar simulations few years ago with GEANT4 10.6 and the behavior with this version was as expected. With the 10.6 version I had to use Factor=1000 to see muon pairs ( photons energy=300 MeV, target 1cm graphite).

Could you please let me know if something in the behavior has changed?

Thanks
Armen

2

Thank you Armen for this report. In new patches the fix will be introduced.

VI

3

Hi Vladimir,
Thank you very much.