Created attachment 748 [details] demonstration of the problem (generated by using TestEm5): energy loss distribution of 100 MeV electrons in 5.6 [um] Silicon target Using Geant4-11.0 for modelling energy loss distributions in thin target the result found to be less accurate than the earlier versions. Anna Zaborowska drew my attention to this issue that pointed to the modifications done in the G4UniversalFluctuation model in version 11.0. The problem can be reproduced easily by using TestEm5 for simulating the energy loss distribution in 5.6 [um] Silicon target by 100 [MeV] electrons. As it can be seen in the attached figure, Geant4-10.7 gives a nice agreement with the available experimental data while Geant4-11.0 can reproduce this results only when rolling back the G4UniversalFluctuation model to that of version 10.7. There is an open MR that (https://gitlab.cern.ch/geant4/geant4-dev/-/merge_requests/2524)that already deals with this issue.
Hi Mihaly, can you, please, check the current master? If this test will not improve situation significantly, then we will change configuration for Opt4 EM physics in a way that the old fluctuation model is used. Vladimir
Created attachment 751 [details] updated plot including the current master result Hi Vladimir, You can find the plot attached updated now with the results obtained by using the current master (as of 25th February 2022). Cheers, Mihaly
Hi, Mihaly, Thanks! So, the improvement is significant but still the 10.7 model is better. So, let us include 10.7 variant of the model into Opt4 EM physics for e+-, mu+-, pi+-, p, pbar. Vladimir
