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Forum: Physics List
Re: None physics list for HE astrophysics applications (Stephan Zimmer)
Date: 07 Sep, 2017
From: Alberto Ribon <Alberto Ribon>

Hello,

all the three physics lists - FTFP_BERT, QGSP_BERT, QGSP_FTFP_BERT - use FTF (Fritiof string model) at low energies, whereas at high energies only the first one (FTFP_BERT) still uses FTF, whereas the other two (QGSP_BERT and QGSP_FTFP_BERT) use QGS (Quark-Gluon-String model).

Regarding the "high-energy" behaviour, both string models (FTF and QGS) formally work up to 100 TeV, but they can't be accurate above ~5 TeV (incident hadron kinetic energy in the lab frame), because gluon (jet) production is not simulated. We think that up to few TeV, both string model should be "reasonable". In principle, QGS model, being more theory-based than the phenomenological FTF model, should be better than FTF above ~1 TeV, but this is not guaranteed in the current versions of Geant4, because the implementation of QGS in Geant4 is still under development.

In conclusion, Geant4 unfortunately cannot guarantee to provide realistic simulations of hadronic interactions in the multi-TeV region, with any physics list.

Regards,
         Alberto

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