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Forum: Hadronic Processes
Re: Question Angular distribution from Hadronic process (Pierre Morfouace)
Date: 18 Jul, 2016
From: Michael H. Kelsey <Michael H. Kelsey>

On Tue, 12 Jul 2016 15:21:10 GMT, Pierre Morfouace wrote:
> I simulate 60 MeV proton into 1 mm of natural tin and I look at the
> angular distribution using different physics list.
> First of all when I use only a physics list with the multiple scattering
> I have the expected behavior with a gaussians a low theta and a
> Rutherford tail for larger theta. However I want to use hadronic
> processes, so in a second step I loaded the HadronicElastic process as
> well as the Binary cascade using the Tripathi and Shen cross section
> parametrization and I was expecting a drop of the number of counts after
> the grazing angle while the behavior is similar to the multiple
> scattering one up to 30 degrees and the counts become higher at larger
> angle (I attached the picture here: red for only MSC and blue for
> MSC+hadronic process).
> Should I load another specific physics list or cross section to see the
> drop in the number of counts around the grazing angle?

What exactly are you counting? Is this total number of tracks vs. angle? If so, then what you see is expected. The inelastic process (which uses the Binary Cascade model) will always produce more than one outgoing particle per incident projectile. Hence, you'll see "more counts" (i.e., more secondaries) whenever that process occurs. If you normalize to number of counts per event, you should see the "1 vs. N" distinction more clearly.

If you want to get more detail in your counting, you could use a SteppingAction rather than a scorer. With that, you can interrogate each track as to the process which created it, the process which caused the step, and whether the track is the original primary or is a newly created secondary. I think what you'll find is that your the population corresponding to your red (MSC) plot are initial primaries, while the blue (inelastic) plots are all secondaries from nuclear interaction.

  -- Michael Kelsey

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