What causes the large difference in the number of GEM calculation after two QMD calculations?

G4QMDReaction.cc (27.8 KB) question.pdf (69.2 KB)

Dear all,

I’m writing this post to ask you about discrepancy between G4QMD and JQMD. My question is why the number of GEM calculation following both QMD models is different as the attached file (question.pdf).

The comparison of neutron thick target yields (TTY) from 290 MeV/u Ar-40 + C for both QMD models is shown in page 1.

TTY of G4QMD+GEM is greater than that of JQMD+GEM below 10 MeV. In the energy range, neutron emission by the GEM model is dominant. I guess the discrepancy comes from the difference of excitation energy of fragments generated at QMD calculation.

I checked distribution of excitation energies after QMD process as shown in page 2. The average excitation energy is almost same in two QMD models. On the other hand, the number of GEM calculation is largely different. The discrepancy of the number of neutrons below 10 MeV comes from the number of GEM calculation.

I don’t find the origin of the discrepancy. I appreciate if you could suggest the reason of the discrepancy.

The way I check the excitation energy of fragments is introduced in attached file (G4QMDReaction.cc).
I added following sentences from line number 522 to 525.

std::ofstream ofs(“excitation.txt”, std::ios::app);
ofs << "charge mass : " << iz << " " << ia << G4endl;
ofs << "excitation energy [MeV] : " << (*it)->GetExcitationEnergy() * GeV << G4endl;

Thank you for your cooperation.

I’ll leave the physics to the experts, but to help them could you please let us know:

  1. Which version of Geant4 this is
  2. Which physics list (standard or custom) you are using

Dear bmorgan,

Thank you for your reply.

  1. I use Geant4 ver.10.06.p01
  2. PhysicsList.cc is attached.

Thank you for your help.

PhysicsList.cc (19.2 KB)

Thanks @sugiken, that’s great!