Dear Experts,
As I know minimum energy for muon generation is 200MeV, I tried to run a simple code to test it, But I can not find any muons when the energy of source is below 900MeV.
this is my input file:
E3T30P.flair (2.5 KB)
Best regards
Mohammad
Dear Mohammad,
I see you have 770-MeV photons on lead. One would indeed expect to see muon pair production, since the photon energy exceeds ~200 MeV, i.e. twice the muon mass which is the threshold for muon pair production in the field of a heavy nucleus.
FLUKA accounts for coherent muon pair production only (in spite of the more permissive description of the manual, which shall be updated accordingly). While this channel exhausts most of the muon pair production cross section at higher energies (where the cross section is sizeable), at lower energies it may fall short, and in your particular case even drop to zero.
Instead, muon production in your problem is dominated by other processes: a photon undergoing a photonuclear interaction, leading to pion production and subsequent decay into muons.
To activate this process, it suffices to pass a PHOTONUC card with emtpy SDUM requesting photonuclear interactions in your material of interest (Pb) and to bias the mean free path for nuclear inelastic interactions of photons by means of the LAM-BIAS card.
With kind regards,
Cesc
Dear @cesc ,
Thanks so much for replying.
My problem is absolutely muons number is zero even(700 MeV), and It starts muon generation for the energy of beam around 1GeV.
So my question is there any limitation in the Fluka model or is it is correct and it is not about the model that implemented in Fluka?
Because I need to know, this issue is the simulation side or physics side.
Best regards,
Mohammad
Also I forgot mention about setting I actives all type muons generation :
For SDUM = MUMUPAIR/MUMUPRIM:
WHAT(1) : flag to switch on muon pair production by photons:
= -1: resets to default (no muon pair production)
= 0: ignored
> 0: interpreted as ich + iqe * 10 + iin * 100 + ids * 1000
where ich = 1 to activate muon pair coherent production
iqe = 1 to activate muon pair incoherent quasielastic production
iin = 1 to activate muon pair incoherent inelastic production
ids = 1 to activate muon pair deep inelastic production
and each is = 0.0 otherwise
Default: no muon pair production by photonsHello,
The reply above answers your questions.
My problem is absolutely muons number is zero even(700 MeV), and It starts muon generation for the energy of beam around 1GeV. So my question is there any limitation in the Fluka model or is it is correct and it is not about the model that implemented in Fluka?
See this quoted paragraph from the reply above:
FLUKA accounts for coherent muon pair production only (in spite of the more permissive description of the manual, which shall be updated accordingly). While this channel exhausts most of the muon pair production cross section at higher energies (where the cross section is sizeable), at lower energies it may fall short, and in your particular case even drop to zero.
Thus, in the FLUKA cross section there are contributions missing, hence the artificial threshold effect at 900 MeV.
Also I forgot mention about setting I actives all type muons generation
See the first sentence quoted above:
FLUKA accounts for coherent muon pair production only (in spite of the more permissive description of the manual, which shall be updated accordingly)
Even if you can request other channels at input, only coherent muon-pair production is ever active.
Finally, if you’re interested in muon production, please consider these paragraphs from the reply above:
Instead, muon production in your problem is dominated by other processes: a photon undergoing a photonuclear interaction, leading to pion production and subsequent decay into muons.
To activate this process, it suffices to pass a PHOTONUC card with emtpy SDUM requesting photonuclear interactions in your material of interest (Pb) and to bias the mean free path for nuclear inelastic interactions of photons by means of the LAM-BIAS card.
Cesc