I currently face the following problem: I have an external generator that, given a kaon 4-momentum, returns the momenta of the daughter particles for some decay channel (e.g. K->pi+pi0). I call this generator in my PrimaryGeneratorAction class (which is the concrete implementation of G4VUserPrimaryGeneratorAction) with the momentum of the kaon at its production. The problem is that the kaon decays in-flight after some 100 meters from its production point. Hence, the momenta of the daughter particles are not the ones in my generator since, from what I understand, Geant boosts again the daughters from the kaon’s initial frame to the its final frame.
My question is: is there any way to retrieve the beamparticle mometum at its decay point inside PrimaryGeneratorAction?
Thank you very much in advance!