Differences in neutron yield between different versions

Dear experts,

I am doing a simulation where I measure the number of neutrons emitted backwards by an 11 GeV electron beam through a 13.4 cm thick lead.

The number of neutrons obtained from this simulation for each version is as follows.

10.4.2 : 96,071, 10.7.2 : 181,246, 11.1.1 : 120856

Between versions 10.4.2 and 10.7.2, it seems to be the effect of the update to the lowEGammaNuclear model in 10.7.0.
However, the tail of the low-energy peak completely reduced in 11.1.1.
Please tell me if you know what is the cause and which result is more consistent with reality.
I’m using QGSP_BERT_HP physicslist for this.


_Geant4 Version:_10.4.2, 10.7.2, 11.1.1
Operating System: Centos7
Compiler/Version: gcc 8.3.1
CMake Version: 3.18.2