Dear G4 team, I have a G4 code that is used to count reactions. It is quite similar to HADRONIC03 example except that I do not kill the particles after the first interaction. I am sending neutrons in tungsten material for instance, using G4NDL4.6 and QGSP_BIC_HP physics list. I tried both geant4.10.7 and geant4.11beta versions. I tried with and without adjusting the final state but the result is similar. It seems that for some inelastic interactions, the recoil nucleus is missing. This leads to unbalanced reactions such as the one below: W184 + neutron -> 2 gammas + 3 neutrons We can easily construct a minimal example based on HADRONIC03 following the steps I described in my second post (https://geant4-forum.web.cern.ch/t/reactions-not-balanced-because-no-residual-is-produced/5468) Please let me know how to fix this. Best, Thomas
Dear Thomas, In some reaction types the ParticleHP (or NeutronHP) model does not produce the recoil nucleus. We will try to improve the code to increase the number of cases (reaction types) in which residual nuclei are produced. In any case, please note that the ParticleHP model does not, in general, conserve energy, momentum and barionic number "event by event". When using QGSP_BIC_HP you are activating the ParticleHP model (that's the meaning of "*_HP") for the neutron transport below 20 MeV. Above 20 MeV Geant4 is using the BIC model, which produces recoil nuclei in all the cases (and also preseves energy and momentum at every nuclear reaction). This is the reason why you observe the lack of recoil nuclei only in "secondary" interactions, since your source are 100 MeV neutrons. Best regards, Emilio Mendoza
