Propagation of ions

[michael-pitt]

In the current version, ion (particles with pdgId = 100AAAZZZI) and status = 1 fail to be appropriately treated by the ddsim.
Keeping the ions and simulating their propagation in G4 is an important feature in studying incoherent processes in eA collisions and beam backgrounds.

Looks like #920 tries to handle with ions, but I not sure if this is the case.

Thanks,
Michael

[andresailer]

Hi @michael-pitt

Yes, #920 should treat ions correctly as long as they are not excited (I==0). And in its current incarnation will treat ions with I>0 the same as if they were not excited. So far we have been unable to understand where to obtain the necessary information from in cases of I>0.
(See also the issue #918. and https://geant4-forum.web.cern.ch/t/g4iontable-findion-with-excitation-level-nullptrs/9224)

[michael-pitt]

Hi @andresailer ,
Thanks for quick answer! Do you have an estimate of when #920 can be ready to be merged? Some MC generators for Heavy Ion collisions produce such particles at the final state, and this RP would be essential for a large community.

Regards,
Michael

[andresailer]

Hi @michael-pitt

That really depends how important these excited states are for the correctness of the simulation. At the moment I have no idea how to treat those correctly. Otherwise the simulation runs OK...

Let me try pushing our Geant4 colleagues for an answer...

[michael-pitt]

Hi @andresailer.

In the meantime, maybe the current implementation can be merged? Otherwise, we cannot use DD4hep with the eA simulations. This solution for excited ions may be a good approximation for the propagation of ion remnants in a magnet field, as we only use A/Z and ion energy.

[andresailer]

OK, I will clean up the merge request and print some warnings when excitation levels cannot be accommodated.

[andresailer]

@michael-pitt Would you like to review #920 ?

[michael-pitt]

Hi @andresailer, I will try to test it with our simulation software. adding @kkauder @wdconinc maybe they can take a look as well.

Thanks a lot!

[wdconinc]

Confirming that #920 works in our context and I think this issue can be considered resolved when #920 is merged. We'll be testing this at scale over the weekend and there may be an appendix if we notice that somehow excited ions are created.