Pi0 yield from 8-GeV proton beam on a thick steel target

Dear all,
I simulated the interaction of a 8-GeV proton beam on a thick steel target, and I sample the production of pi0 meson, computing the differential yield dN / dE * 1/POT, where “E” is the meson energy and POT is the number of protons on target.
I tested different physics list. The colors are referring to the plots in the following. I used g4 version 4.10.02.p02

Black: FTFP_BERT_HP physics list
Red: QGSP_BERT_HP physics list
Green: QGSP_BIC_HP physics list

I also made a FLUKA simulation (blue), using the latest Fluka version: 2011.2x.8
Finally, I considered the result of an analytic model (Sanford-Wang), in magenta

I report the comparison of these calculations.

comparison.pdf (38.8 KB)
comparisonZoom.pdf (19.2 KB)

As you see, there are significant discrepancies among the different models, that I’d like to share with you to get a feedback about this. In particular, there is a good reason to select a specific physics list for this energy range?


the difference may be understand looking into Physics List configurations for Geant4 10.2:

FTFP_BERT - FTF model is used for protons at 8 GeV;

QGSP_BERT - the Bertini cascade is used at 8 GeV;

QGSP_BIC - the Binary cascade is used at 8 GeV.

The low energy part of spectra (below 1 GeV) FTF and the Binary cascade use similar sub-model, which is different from the Bertini Cascade.

High energy part of spectra for FLUKA, Binary, and Bertini not identical but similar. I cannot comment analytical model, usually such models are very approximate.


Dear VI,
thanks for your message. I agree that the differences are due to the different models used for the simulations. Do you know what is the preferred model to use for this beam energy (in other words, is there a model that is known to better reproduce thick-target data in this energy regime)?