Dear FLUKA experts!

Up to now you have all been of great help to me. I have encountered an interesting result in my simulations and would like to seek your expertise once again.

Just to repeat what I am doing: I am simulating an electron beam of 3.2GeV imping on a tungsten target (0.1X0 thickness). The output data I process with a c++ program and plot the results using root histograms.

I will include my mgdraw_empty.f user routine and also my myfluka.inp files as well as the processing program called plotting.cc for you to understand what I am doing.

mgdraw_empty.f (11.5 KB)

myfluka.inp (1.1 KB)

plotting.cc (14.2 KB)

As a study for the experiment I am working on, the angular distributions of outgoing hadrons are very important. Thus I am using the momenta of the outgoing hadrons of electronuclear interactions (ICODE=101) to determine their angles. Intuitively an isotropic distribution of theta for radiated hadrons of electronuclear interactions with small beam energies (close to 0GeV) makes sense. For larger energies I would assume the shape to change and shift towards smaller angles (due to the large boost in z-direction coming from the beam particle).

If I take different beam energies in FLUKA this result cannot be seen. For beam energies of 3.2GeV, 30GeV and 300GeV the theta distribution shifts only very vaguely contrary to what I would think would happen. The red sine in the plots indicates the isotropic sine-distribution.

My intuitive expectation would look more like this (simple python simulation of isotropic distributed points on sphere with Lorentz boost along z axis):

Since I have no access to the source code and do not know how FLUKA simulates and handles these hadrons from electronuclear interactions, I would be happy for any help or explanation!

Thanks in advance,

Laney Klipphahn