Problem 2558

Summary: Unexpected Dependency of Neutron Energy Deposition with QBBC Physics List in Geant4 11.1.2 and latest master HEAD
Product: Geant4 Reporter: Dmitri Konstantinov <Dmitri.Konstantinov>
Component: physics_listsAssignee: Vladimir.Ivantchenko
Status: ASSIGNED ---    
Severity: minor CC: Vladimir.Ivantchenko
Priority: P4    
Version: other   
Hardware: All   
OS: All   
Attachments: Neutron Energy Deposition vs. Starting Distance Plot.

Description Dmitri Konstantinov 2023-08-21 11:15:58 CEST 
Created attachment 820 [details]
Neutron Energy Deposition vs. Starting Distance Plot.

[Created from Geant4 user forum: https://geant4-forum.web.cern.ch/t/neutron-distance-dose-dependency/10950

Using the **QBBC** physics list in Geant4 v11.1.2, an unexpected behavior was observed during a simulation measuring the deposited energy by neutrons in a water ball (r=15cm). While protons showed consistent results, neutrons presented an unexpected dependency on Edep with z. The water ball is centrally placed in an empty (G4_Galactic) mother volume.

The simulation was run using a point-like, monoenergetic beam (Ebeam = 1 GeV) along the z-axis with random initial positions z ranging from just before the surface (16cm) to 1 meter from the center of the ball.

Based on git bisect, it appears that the issue might have been introduced in the MR 2976: "phys-ctor-hinelastic-V11-00-01 et al.: enable neutron general process in QBBC + added process of muon pair production by muons"

https://gitlab.cern.ch/geant4/geant4-dev/-/merge_requests/2976