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None Problems with ParticleHP for proton inelastic 

Forum: Hadronic Processes
Date: 30 Mar, 2017
From: Hesse <Hesse>

Hi

I am using Geant4 10.02 with the vGate interface. I downloaded the TENDL library to study the radioisotope production and neutron emission from the O18+proton reaction. I am using the QGSP_BIC_AllHP physics list.

To understand how Geant4 was managing the proton interactions I looked into the source code. I was surprised by what I found: if i am not mistaken, the inelastic proton interactions are not treated as outgoing channels with multiple particles, but directly sorting possible outgoing particles independantly. To make it clearer with an example: in place of sorting randomly (according to cross sections) for example between the outgoing n+F18 and n+alpha+N15 channels, the code seems to sort randomly if a n will be produced, then if an alpha will be produced, and so on! Maybe this philosophy make sense in high energy physics, but this seems strange at low energy (< 50 MeV).

I think there also is a problem with the energy of outgoing particles in the ParticleHP: the Qvalue is not taken into account ! When testing by forcing the reaction O18(p,n+alpha)N15, I got neutrons up to the kinetic energy of the protons, which should be impossible because the (p,n+alpha) reaction is endothermic (QV=-6.9 MeV). This problem could come from the fact that ParticleHP was derived from NeutronHP for which only positive Qvalues are expected.

Hopefully someone will be able to prove me wrong (browsing through the Geant4 code is no easy task) or maybe corrections have been implemented in more recent releases (I am using the latest release available with vGate).

Best regards,

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