Problem 2530

Summary: Unusual behaviour for the "AddEmRegion" macro command
Product: Geant4 Reporter: ronny.stanzani
Component: processes/electromagneticAssignee: Vladimir.Ivantchenko
Status: RESOLVED FIXED    
Severity: normal CC: daren.sawkey, paolo.dondero
Priority: P4    
Version: 11.1   
Hardware: Other   
OS: Linux   
Attachments: The macro (sandia.mac) containing the modified commands.

Description ronny.stanzani 2023-02-13 09:56:11 CET
Created attachment 802 [details]
The macro (sandia.mac) containing the modified commands.

Test setup:
TestEm11 example with Geant4 11.1. I modified the sandia.mac macro to launch 100 keV protons with "/testem/applyAutomaticStepMax false" setting and "/tracking/verbose 1" to see details of processes happening. 
When I try different combinations of Physics Lists, the following behaviour occurs: 

1. if I use emstandard_opt4, I see mainly msc and hIoni processes;
2. if I use emstandardSS, I see mainly coulombscat;

Both those behaviours seems ok to me. But:

3. if I use emstandard_opt4 and the command "/process/em/AddEmRegion DefaultRegionForTheWorld G4EmStandardSS", I see only hIoni processes (no scattering at all). This seems a bit strange to me.

As test purpose, if I increase the protons energy (to about 1000 keV) in case 3, coulombscattering appears.

Could this behaviour be related to the MscThetaLimit parameter? If I set MscThetaLimit to zero in PhysicsList.cc, coulombscattering appears also at 100 keV. It seems that the command "AddEmRegion" does not change the theta limit.