Understimating neutron flux

Hey everyone,

I am using GEANT4 simulation for finding neutron fluxes from various targets when electron beam strikes them. I see a pattern that the value of neutron flux that I am getting through GEANT4 is less than the literature suggests (various work done and published in renowned journals).
I am told MC simulations tend to underestimate the absolute values of particle fluxes sometimes by a power of 10. I am not very convinced. Does anyone else face this issue?
I am using QGSP_BIC_HP physics list and for material definition I am using NIST data.

Any help would be much appreciated.


we have so far only one model of electro-nuclear interation and only one cross section, which are used in all Physics Lists. Secondary neutron transport a bit different between QGSP_BIC and QGSP_BIC_HP. Would you be able to show neutron spectra after a target this known data and Geant4 prediction?