Range of low-energy muons changed between 11.0.p0 and 11.2.p01

In the simulation of the Mu3e experiment we see that the range of muons at p=27.5 MeV/c in Mylar is reduced by about 100 um when changing from 11.0.p0 to 11.2.p01. We have reproduced this on several linux machines using different versions of gcc. Our muon physics setup is posted below. Is this expected by some change in the models/tables? Note that the old simulations (11.0. and earlier) agree well with measurements at PSI.
Best regards
Nik


    else if(particleName == "mu+"
         || particleName == "mu-"
         || boost::starts_with(particleName, "mu+/")
    ) {
        helper->RegisterProcess(getScatteringProcess(msmodel), particle);

        //helper->RegisterProcess(new G4MuMultipleScattering, particle);
        helper->RegisterProcess(new G4MuIonisation, particle);
        helper->RegisterProcess(new G4MuBremsstrahlung, particle);
        helper->RegisterProcess(new G4MuPairProduction, particle);

        auto muonNuclearProcess = new G4MuonNuclearProcess();
        muonNuclearProcess->RegisterMe(new G4MuonVDNuclearModel);
        helper->RegisterProcess(muonNuclearProcess, particle);
    }

Hello, Nik,

nothing was expected to be change for range of muons.

Please, try to do few simple checks: 1) compare properties of Mylar in these two versions, criticals are density and mean ionisation potential; 2) infor us what is used as a multiple scattering model; 3) try to use $G4INSTALL/examples/extended/electromagnetic/TestEm5, use G4_MYLAR as a target and reproduce the effect (this run very fast, more time will be needed to switch the G4 version than to run).

After these checks we may decide if there is a subject for Bugzilla bug report.

VI

Hi,
thanks for the quick response. I see no difference in the properties of Mylar between the two versions. We use the Urban model for multiple scattering. I now ran TestEm5 with Mylar and emstandard_opt0 as physics and also there see a difference in range - 825 um in 11.0.0 to 623 um in 11.2.1. I have attached the output of both runs, I hope this helps with further diagnosis.
Thanks
Nik

output_11_0.txt (75.3 KB)
output_11_2_1.txt (73.5 KB)

Is there any other input you need? How would I go about filing a bug report?
Many thanks
Nik