Confirming Validation of Proton-Induced Spallation on Lead Target Histogram


Just wanted to confirm if my simulation results made sense.

I am validating a simple proton-induced spallation event on a 10 cm diameter x 60 cm length lead target. I am attempting the validate the mean number of neutrons yielded per proton with Intense Neutron Generator results.

I understand that since Geant4 is a Monte-Carlo based approach, I can expect many events where the incident proton does not result in any interactions with the target nuclei and will produce no protons. In fact, the mean number of neutrons generated per proton agrees with the experimental results from the ING.

However, in this histogram, which shows the number of neutrons generated per proton and that frequency, we can see that there is a large spike for “0 neutrons” generated per proton. Again, with the cross section of spallation and the Monte Carlo approach, I am assuming that this is normal - yet I wanted to make sure that this artifact isn’t something more serious, like a fault in my code or some sort of issue with the physics list.

Thank you all for the help!

Edit: Missing labels on the histogram, but the Y-Axis is neutrons generated per proton, and the X-axis is frequency.

Geant4 Version: 11.2.1
Operating System: RockyLinux 9.3 (Official Geant4 VM)