Physics Issue in the changed geometry


Respected Allpix Developers,

We were successful in developing our own geometry through GDML import. However when we use QGSP_BERT_HP physics we get the following error(attached pic). This error is only there when we use the _HP option. We tried this with QGSP_BERT. That works fine.

Can you please recommend us something to resolve this.


Dear Sanchit,

I’m not entirely sure what you mean by “solved via GDML import”. The exact sensor Geometry has to be known to Allpix Squared in order to perform the charge transport properly.

However, your problem has nothing to do with Allpix Squared. Reading the error message provided by Geant4 above tells you, that it doesn’t know how to treat neutrons in the given material. Reasons are either that the G4NEUTRONDATA are missing (unlikely as we check for it) or that the material you use has no cross-section tables available. The error message also suggests contacting the G4 hadron group.

Best regards