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I have a problem decaying neutrons. I am interested in simulating the beta decay of neutron at rest: n -> p e- nu
I use examples/extended/electromagnetic/TestEm5 as a template.
OK, in order to set the global time at zero at decay I set the neutron lifetime to a very small value:
/particle/select neutron /particle/property/stable false /particle/property/lifetime 1.E-20
It works and my neutron decays essentially instantaneously.
The problem is, the final-state proton is never tracked, actually it never appears as a decay product at all if the initial neutron kinetic energy is zero. The electron and neutrino are handled correctly and appear on the stack. I check it by printing the global times, energies, particles' ID from the SteppingAction.cc
Only if I set the initial neutron kinetic energy to non-zero, proton appears.
I have the following user cuts in DetectorConstruction
G4double theMaxStepSize = 0.1 * mm; G4double theMaxTime = 0.001 * s; G4double theMinEkine = 1.0 * eV;
logicWorld->SetUserLimits (new G4UserLimits(theMaxStepSize, DBL_MAX, // theMaxLengthCut theMaxTime, // theMaxTimeCut theMinEkine));
I check that if a particle selected in the PrimaryGeneratorEvent.cc is the proton, it is tracked if its kinetic energy is above 1 eV. But it is not put on stack if proton_KE< 1 eV, regardless of my seting of theMinEkine?
My question: because in the neutron decay at rest, the proton kinetic energy is up to 0.8 keV, why it is NEVER put on a stack in the decay process? What is the variable, a cut, I am not setting right?
Cheers, Emil Frlez
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